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 A306791 #6 Mar 10 2019 11:27:49
%S A306791 2,9,35,335,7709,510743
%N A306791 Number of distinct eigenvalues of n X n matrices with elements {-1, 1}.
%H A306791 S. E. Thornton, <a href="http://www.bohemianmatrices.com/cpdb/unstructured/unstructured_n1_1">Properties of the Bohemian family of n x n matrices with population {-1, 1}</a>, Characteristic Polynomial Database.
%Y A306791 Number of characteristic polynomials is in A272662.
%Y A306791 Number of minimal polynomials is in A306782.
%K A306791 nonn,more,hard
%O A306791 1,1
%A A306791 _Steven E. Thornton_, Mar 10 2019