The graph with spectrum 141 240 (−4)10 (−6)9
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- Blokhuis, A., Brouwer, A.E. & Haemers, W.H. Des. Codes Cryptogr. (2012) 65: 71. doi:10.1007/s10623-011-9529-6
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We show that there is a unique graph with spectrum as in the title. It is a subgraph of the McLaughlin graph. The proof uses a strong form of the eigenvalue interlacing theorem to reduce the problem to one about root lattices.