Appendix 1: Basic subcode chains for \(n = 42, 43, 45, 47\)
1.1
\(n = 42\)
$$\begin{aligned}&W_{\mathcal {C}_{42, 18}}(x) =357x^{32} + 12600x^{28} + \cdots + 39522x^{16} + 2744x^{12} + 1.\nonumber \\&W_{\mathcal {C}^{\perp }_{42, 18}}(x) =x^{42} + 48x^{35} + \cdots + 420x^{8} + 48x^{7} + 1. \end{aligned}$$
(7)
$$\begin{aligned}&T^{(42)}_{13 \times 18} = \left( \begin{array}{c|c} 1000000000000 &{} 01010\\ 0100000000000 &{} 00010\\ 0010000000000 &{} 01001\\ 0001000000000 &{} 01111\\ 0000100000000 &{} 10101\\ 0000010000000 &{} 11110\\ 0000001000000 &{} 10001\\ 0000000100000 &{} 01100\\ 0000000010000 &{} 01000\\ 0000000001000 &{} 10000\\ 0000000000100 &{} 00000\\ 0000000000010 &{} 00000\\ 0000000000001 &{} 10000\\ \end{array}\right) . \end{aligned}$$
(8)
$$\begin{aligned}&W_{\mathcal {C}_{42, 13}}(x) =3x^{32} + 420x^{28} + \cdots + 1296x^{16} + 60x^{12} + 1.\nonumber \\&W_{\mathcal {C}^{\perp }_{42, 13}}(x) =x^{42} + 114x^{37} + \cdots + 640x^{6} + 114x^{5} + 1. \end{aligned}$$
(9)
1.2
\(n = 43\)
$$\begin{aligned} W_{\mathcal {C}_{43, 19}}(x)&=8x^{36} + 1365x^{32} + \cdots + 62930x^{16} + 3808x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{43, 19}}(x)&=x^{43} + 8x^{36} + \cdots + 180x^{8} + 8x^{7} + 1. \end{aligned}$$
(10)
$$\begin{aligned} T^{(43)}_{16 \times 19}&= \left( \begin{array}{c|c} 1000000000000000 &{} 101\\ 0100000000000000 &{} 101\\ 0010000000000000 &{} 110\\ 0001000000000000 &{} 111\\ 0000100000000000 &{} 101\\ 0000010000000000 &{} 011\\ 0000001000000000 &{} 000\\ 0000000100000000 &{} 010\\ 0000000010000000 &{} 001\\ 0000000001000000 &{} 001\\ 0000000000100000 &{} 110\\ 0000000000010000 &{} 000\\ 0000000000001000 &{} 001\\ 0000000000000100 &{} 101\\ 0000000000000010 &{} 000\\ 0000000000000001 &{} 000\\ \end{array}\right) , ~ T^{(43)}_{13 \times 16} = \left( \begin{array}{c|c} 1000000000000 &{} 010\\ 0100000000000 &{} 011\\ 0010000000000 &{} 010\\ 0001000000000 &{} 111\\ 0000100000000 &{} 111\\ 0000010000000 &{} 011\\ 0000001000000 &{} 110\\ 0000000100000 &{} 000\\ 0000000010000 &{} 000\\ 0000000001000 &{} 110\\ 0000000000100 &{} 000\\ 0000000000010 &{} 100\\ 0000000000001 &{} 000\\ \end{array}\right) . \end{aligned}$$
(11)
$$\begin{aligned} W_{\mathcal {C}_{43, 16}}(x)&=6x^{36} + 159x^{32} + \cdots + 8020x^{16} + 432x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{43, 16}}(x)&=x^{43} + 118x^{37} + \cdots + 426x^{7} + 118x^{6} + 1.\nonumber \\ W_{\mathcal {C}_{43, 13}}(x)&=14x^{32} + 589x^{28} + \cdots + 1047x^{16} + 33x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{43, 13}}(x)&=x^{43} + 115x^{38} + \cdots + 763x^{6} + 115x^{5} + 1. \end{aligned}$$
(12)
1.3
\(n = 45\)
$$\begin{aligned}&W_{\mathcal {C}_{45, 21}}(x) =220x^{36} + 17325x^{32} + \cdots + 153450x^{16} + 7140x^{12} + 1.\nonumber \\&W_{\mathcal {C}^{\perp }_{45, 21}}(x) =x^{45} + 220x^{36} + \cdots + 2376x^{10} + 220x^{9} + 1. \end{aligned}$$
(13)
$$\begin{aligned}&T^{(45)}_{19 \times 21} = \left( \begin{array}{c|c} 1000000000000000000 &{} 10\\ 0100000000000000000 &{} 10\\ 0010000000000000000 &{} 10\\ 0001000000000000000 &{} 11\\ 0000100000000000000 &{} 00\\ 0000010000000000000 &{} 11\\ 0000001000000000000 &{} 11\\ 0000000100000000000 &{} 10\\ 0000000010000000000 &{} 11\\ 0000000001000000000 &{} 00\\ 0000000000100000000 &{} 11\\ 0000000000010000000 &{} 11\\ 0000000000001000000 &{} 01\\ 0000000000000100000 &{} 11\\ 0000000000000010000 &{} 00\\ 0000000000000001000 &{} 00\\ 0000000000000000100 &{} 10\\ 0000000000000000010 &{} 00\\ 0000000000000000001 &{} 00\\ \end{array}\right) , T^{(45)}_{16 \times 19} = \left( \begin{array}{c|c} 1000000000000000 &{} 011\\ 0100000000000000 &{} 010\\ 0010000000000000 &{} 111\\ 0001000000000000 &{} 011\\ 0000100000000000 &{} 101\\ 0000010000000000 &{} 111\\ 0000001000000000 &{} 100\\ 0000000100000000 &{} 001\\ 0000000010000000 &{} 010\\ 0000000001000000 &{} 110\\ 0000000000100000 &{} 000\\ 0000000000010000 &{} 100\\ 0000000000001000 &{} 000\\ 0000000000000100 &{} 100\\ 0000000000000010 &{} 000\\ 0000000000000001 &{} 000\\ \end{array}\right) .\nonumber \\ \end{aligned}$$
(14)
$$\begin{aligned} W_{\mathcal {C}_{45, 19}}(x)&=34x^{36} + 4473x^{32} + \cdots + 38646x^{16} + 1722x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{45, 19}}(x)&=x^{45} + 108x^{38} + \cdots + 324x^{8} + 108x^{7} + 1.\nonumber \\ W_{\mathcal {C}_{45, 16}}(x)&=7x^{36} + 561x^{32} + 8115x^{28} + \cdots + 4998x^{16} + 169x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{45, 16}}(x)&=x^{45} + 109x^{39} + \cdots + 789x^{7} + 109x^{6} + 1. \end{aligned}$$
(15)
$$\begin{aligned} T^{(45)}_{14 \times 16}&= \left( \begin{array}{c|c} 10000000000000 &{} 01\\ 01000000000000 &{} 00\\ 00100000000000 &{} 01\\ 00010000000000 &{} 10\\ 00001000000000 &{} 11\\ 00000100000000 &{} 11\\ 00000010000000 &{} 01\\ 00000001000000 &{} 10\\ 00000000100000 &{} 00\\ 00000000010000 &{} 10\\ 00000000001000 &{} 00\\ 00000000000100 &{} 10\\ 00000000000010 &{} 00\\ 00000000000001 &{} 00\\ \end{array}\right) . \end{aligned}$$
(16)
$$\begin{aligned} W_{\mathcal {C}_{45, 14}}(x)&=134x^{32} + 2075x^{28} + \cdots + 1255x^{16} + 31x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{45, 14}}(x)&=x^{45} + 65x^{40} + \cdots + 482x^{6} + 65x^{5} + 1. \end{aligned}$$
(17)
1.4
\(n = 47\)
$$\begin{aligned}&W_{\mathcal {C}_{47,23}}(x) = 4324x^{36} + 178365x^{32} + \cdots + 356730x^{16} + 12972x^{12} + 1,\nonumber \\&W_{\mathcal {C}^{\perp }_{47,23}}(x) = x^{47} + 4324x^{36} + \cdots + 12972x^{12} + 4324x^{11} + 1.\end{aligned}$$
(18)
$$\begin{aligned}&T^{(47)}_{20 \times 23} = \left( \begin{array}{c|c} 10000000000000000000 &{} 000\\ 01000000000000000000 &{} 001\\ 00100000000000000000 &{} 111\\ 00010000000000000000 &{} 101\\ 00001000000000000000 &{} 111\\ 00000100000000000000 &{} 011\\ 00000010000000000000 &{} 001\\ 00000001000000000000 &{} 110\\ 00000000100000000000 &{} 011\\ 00000000010000000000 &{} 110\\ 00000000001000000000 &{} 100\\ 00000000000100000000 &{} 010\\ 00000000000010000000 &{} 100\\ 00000000000001000000 &{} 000\\ 00000000000000100000 &{} 000\\ 00000000000000010000 &{} 000\\ 00000000000000001000 &{} 000\\ 00000000000000000100 &{} 000\\ 00000000000000000010 &{} 000\\ 00000000000000000001 &{} 000\\ \end{array}\right) , T^{(47)}_{17 \times 20} = \left( \begin{array}{c|c} 10000000000000000 &{} 000\\ 01000000000000000 &{} 000\\ 00100000000000000 &{} 101\\ 00010000000000000 &{} 010\\ 00001000000000000 &{} 111\\ 00000100000000000 &{} 110\\ 00000010000000000 &{} 101\\ 00000001000000000 &{} 101\\ 00000000100000000 &{} 111\\ 00000000010000000 &{} 110\\ 00000000001000000 &{} 010\\ 00000000000100000 &{} 000\\ 00000000000010000 &{} 100\\ 00000000000001000 &{} 100\\ 00000000000000100 &{} 000\\ 00000000000000010 &{} 000\\ 00000000000000001 &{} 000\\ \end{array}\right) .\nonumber \\ \end{aligned}$$
(19)
$$\begin{aligned} W_{\mathcal {C}_{47, 20}}(x)&=516x^{36} + 22461x^{32} + \cdots + 44922x^{16} + 1548x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{47, 20}}(x)&=x^{47} + 63x^{40} + \cdots + 315x^{8} + 63x^{7} + 1.\nonumber \\ W_{\mathcal {C}_{47, 17}}(x)&=82x^{36} + 2721x^{32} + \cdots + 5694x^{16} + 162x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{47, 17}}(x)&=x^{47} + 84x^{41} + \cdots + 483x^{7} + 84x^{6} + 1. \end{aligned}$$
(20)
$$\begin{aligned} T^{(47)}_{14 \times 17}&= \left( \begin{array}{c|c} 10000000000000 &{} 000\\ 01000000000000 &{} 000\\ 00100000000000 &{} 101\\ 00010000000000 &{} 101\\ 00001000000000 &{} 011\\ 00000100000000 &{} 010\\ 00000010000000 &{} 010\\ 00000001000000 &{} 001\\ 00000000100000 &{} 100\\ 00000000010000 &{} 000\\ 00000000001000 &{} 010\\ 00000000000100 &{} 100\\ 00000000000010 &{} 000\\ 00000000000001 &{} 000\\ \end{array}\right) . \end{aligned}$$
(21)
$$\begin{aligned} W_{\mathcal {C}_{47, 14}}(x)&=5x^{36} + 346x^{32} + \cdots + 707x^{16} + 10x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{47, 14}}(x)&=x^{47} + 88x^{42} + \cdots + 656x^{6} + 88x^{5} + 1. \end{aligned}$$
(22)
Appendix 2: Pairs of nested self-orthogonal codes for \(n = 42,44,46,48\)
1.1
\(n = 42\)
$$\begin{aligned}&W_{\mathcal {C}_{42, 14}}(x) =x^{42} + 3x^{32} + \cdots + 60x^{12} + 3x^{10} + 1.\nonumber \\&W_{\mathcal {C}^{\perp }_{42, 14}}(x) =x^{42} + 640x^{36} + \cdots + 14580x^{8} + 640x^{6} + 1. \end{aligned}$$
(23)
$$\begin{aligned}&W_{\mathcal {C}_{42, 13}}(x) =3x^{32} + 420x^{28} + \cdots + 1296x^{16} + 60x^{12} + 1.\nonumber \\&W_{\mathcal {C}^{\perp }_{42, 13}}(x) =x^{42} + 114x^{37} + \cdots + 640x^{6} + 114x^{5} + 1. \end{aligned}$$
(24)
1.2
\(n = 44\)
$$\begin{aligned}&W_{\mathcal {C}_{44, 14}}(x) =x^{44} + 47x^{32} + \cdots + 1636x^{16} + 47x^{12} + 1.\nonumber \\&W_{\mathcal {C}^{\perp }_{44, 14}}(x) =x^{44} + 878x^{38} + \cdots + 21844x^{8} + 878x^{6} + 1. \end{aligned}$$
(25)
$$\begin{aligned} T^{(44)}_{13 \times 14}&= \left( \begin{array}{c|c} 1000000000000 &{} 1\\ 0100000000000 &{} 0\\ 0010000000000 &{} 1\\ 0001000000000 &{} 0\\ 0000100000000 &{} 1\\ 0000010000000 &{} 1\\ 0000001000000 &{} 0\\ 0000000100000 &{} 0\\ 0000000010000 &{} 0\\ 0000000001000 &{} 0\\ 0000000000100 &{} 0\\ 0000000000010 &{} 0\\ 0000000000001 &{} 0\\ \end{array}\right) . \end{aligned}$$
(26)
$$\begin{aligned} W_{\mathcal {C}_{44, 13}}(x)&=29x^{32} + 818x^{28} + \cdots + 818x^{16} + 18x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{44, 13}}(x)&=x^{44} + 132x^{39} + \cdots + 878x^{6} + 132x^{5} + 1. \end{aligned}$$
(27)
1.3
\(n = 46\)
$$\begin{aligned} W_{\mathcal {C}_{46, 20}}(x)&=x^{46} + 34x^{36} + \cdots + 1722x^{12} + 34x^{10} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{46, 20}}(x)&=x^{46} + 432x^{38} + \cdots + 8404x^{10} + 432x^{8} + 1.\nonumber \\ W_{\mathcal {C}_{46, 19}}(x)&=17x^{36} + 889x^{34} + \cdots + 833x^{12} + 17x^{10} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{46, 19}}(x)&=x^{46} + 116x^{39} + \cdots + 432x^{8} + 116x^{7} + 1. \end{aligned}$$
(28)
$$\begin{aligned} T^{(46)}_{19 \times 20}&= \left( \begin{array}{c|c} 1000000000000000000 &{} 1\\ 0100000000000000000 &{} 1\\ 0010000000000000000 &{} 1\\ 0001000000000000000 &{} 1\\ 0000100000000000000 &{} 0\\ 0000010000000000000 &{} 0\\ 0000001000000000000 &{} 1\\ 0000000100000000000 &{} 0\\ 0000000010000000000 &{} 1\\ 0000000001000000000 &{} 0\\ 0000000000100000000 &{} 0\\ 0000000000010000000 &{} 0\\ 0000000000001000000 &{} 0\\ 0000000000000100000 &{} 0\\ 0000000000000010000 &{} 0\\ 0000000000000001000 &{} 0\\ 0000000000000000100 &{} 0\\ 0000000000000000010 &{} 0\\ 0000000000000000001 &{} 0\\ \end{array}\right) , T^{(46)}_{14 \times 15} = \left( \begin{array}{c|c} 10000000000000 &{} 0\\ 01000000000000 &{} 1\\ 00100000000000 &{} 1\\ 00010000000000 &{} 1\\ 00001000000000 &{} 1\\ 00000100000000 &{} 0\\ 00000010000000 &{} 0\\ 00000001000000 &{} 0\\ 00000000100000 &{} 0\\ 00000000010000 &{} 0\\ 00000000001000 &{} 0\\ 00000000000100 &{} 0\\ 00000000000010 &{} 0\\ 00000000000001 &{} 0\\ \end{array}\right) . \end{aligned}$$
(29)
$$\begin{aligned} W_{\mathcal {C}_{46, 15}}(x)&=x^{46} + 31x^{34} + \cdots + 134x^{14} + 31x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{46, 15}}(x)&=x^{46} + 547x^{40} + \cdots + 16127x^{8} + 547x^{6} + 1.\nonumber \\ W_{\mathcal {C}_{46, 14}}(x)&=19x^{34} + 65x^{32} + \cdots + 69x^{14} + 12x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{46, 14}}(x)&=x^{46} + 86x^{41} + \cdots + 547x^{6} + 86x^{5} + 1. \end{aligned}$$
(30)
1.4
\(n = 48\)
$$\begin{aligned} W_{\mathcal {C}_{48, 21}}(x)&=x^{48} + 2064x^{36} + \cdots + 67383x^{16} + 2064x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{48, 21}}(x)&=x^{48} + 378x^{40} + \cdots + 5376x^{10} + 378x^{8} + 1.\nonumber \\ W_{\mathcal {C}_{48, 20}}(x)&=1060x^{36} + 33597x^{32} + \cdots + 33786x^{16} + 1004x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{48, 20}}(x)&=x^{48} + 72x^{41} + \cdots + 378x^{8} + 72x^{7} + 1. \end{aligned}$$
(31)
$$\begin{aligned} T^{(48)}_{20 \times 21}&= \left( \begin{array}{c|c} 10000000000000000000 &{} 1\\ 01000000000000000000 &{} 1\\ 00100000000000000000 &{} 1\\ 00010000000000000000 &{} 1\\ 00001000000000000000 &{} 1\\ 00000100000000000000 &{} 0\\ 00000010000000000000 &{} 0\\ 00000001000000000000 &{} 1\\ 00000000100000000000 &{} 0\\ 00000000010000000000 &{} 0\\ 00000000001000000000 &{} 0\\ 00000000000100000000 &{} 0\\ 00000000000010000000 &{} 0\\ 00000000000001000000 &{} 0\\ 00000000000000100000 &{} 0\\ 00000000000000010000 &{} 0\\ 00000000000000001000 &{} 0\\ 00000000000000000100 &{} 0\\ 00000000000000000010 &{} 0\\ 00000000000000000001 &{} 0\\ \end{array}\right) , T^{(48)}_{14 \times 15} = \left( \begin{array}{c|c} 10000000000000 &{} 1\\ 01000000000000 &{} 1\\ 00100000000000 &{} 1\\ 00010000000000 &{} 1\\ 00001000000000 &{} 0\\ 00000100000000 &{} 0\\ 00000010000000 &{} 0\\ 00000001000000 &{} 0\\ 00000000100000 &{} 0\\ 00000000010000 &{} 0\\ 00000000001000 &{} 0\\ 00000000000100 &{} 0\\ 00000000000010 &{} 0\\ 00000000000001 &{} 0\\ \end{array}\right) . \end{aligned}$$
(32)
$$\begin{aligned} W_{\mathcal {C}_{48, 15}}(x)&=x^{48} + 15x^{36} + \cdots + 1053x^{16} + 15x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{48, 15}}(x)&=x^{48} + 744x^{42} + \cdots + 23130x^{8} + 744x^{6} + 1.\nonumber \\ W_{\mathcal {C}_{48, 14}}(x)&=9x^{36} + 538x^{32} + \cdots + 515x^{16} + 6x^{12} + 1.\nonumber \\ W_{\mathcal {C}^{\perp }_{48, 14}}(x)&=x^{48} + 106x^{43} + \cdots + 744x^{6} + 106x^{5} + 1. \end{aligned}$$
(33)