Erratum to:

Math Semesterber 2020

https://doi.org/10.1007/s00591-020-00288-y

In the published version of this article, on page 9, line 5 underneath formula 20, a typesetting mistake occurred. The corrected formula reads as follows: λ1 ≈ 0.492, λ2 ≈ 2.304 and λ3 ≈ 28.204