This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A171908 #4 Jun 02 2025 02:23:24 %S A171908 20,30,0,10,0,0 %N A171908 a(n)= Number of 5 X 5 permutation matrices with trace n and determinant -1. %e A171908 a(0)=20 because we have 20 different permutation matrices 5 x 5 with trace 0 and determinant -1. %Y A171908 A171806, A171808, A171809, A171906, A171907 %K A171908 fini,full,nonn %O A171908 0,1 %A A171908 _Artur Jasinski_, Dec 31 2009