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 A328159 #12 Apr 11 2020 22:41:00
%S A328159 0,1,3,7,19,72,280,1348,7542,48290,348902,2805666,24797845,238678891,
%T A328159 2482575930,27731295522,330955304428,4201424981020,56521276891669,
%U A328159 803122164193328,12018137424023094,188906053776728602,3111632374404898304,53597059526977558291
%N A328159 Number of n X n matrices (up to permutation of their rows and columns) with entries {0,1,2} with all row and column sums equal to 3.
%C A328159 Also, bipartite cubic multigraphs up to color-preserving isomorphism, with no edges of multiplicity 3.
%e A328159 For n=3 the a(3)=3 solutions are [2,1,0; 1,0,2; 0,2,1], [1,1,1; 2,0,1; 0,2,1] and [1,1,1; 1,1,1; 1,1,1].
%Y A328159 a(n) = A232215(n) - A232215(n-1) for n >= 1.
%K A328159 nonn,hard
%O A328159 1,3
%A A328159 _Brendan McKay_, Oct 05 2019
%E A328159 a(13) corrected and terms a(14) and beyond from _Andrew Howroyd_, Apr 11 2020