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 A232216 #18 Apr 04 2020 17:43:03 %S A232216 1,1,3,9,43,264,2804,44524,1012456,30502320,1166185222,54902972542, %T A232216 3115560948081,209575881782122,16484822517084705,1498893370236782629, %U A232216 155996155818460127750,18424063865105027559797,2450806855748517847761175,364738110721163795332103692,60368334488355648041244493885 %N A232216 Number of non-isomorphic n X n nonnegative integer matrices with all row and column sums equal to 4 up to permutations of rows and columns. %C A232216 Arises from counting of symmetric tensor invariants without color. See Geloun-Ramgoolam, Section 6.2 for information and Mathematica code. %H A232216 Erick Castro, Itzhak Roditi, <a href="https://arxiv.org/abs/1804.08031">A combinatorial matrix approach for the generation of vacuum Feynman graphs multiplicities in phi-4 theory</a>, arXiv:1804.08031 [math-ph], 2018. %H A232216 J. B. Geloun, S. Ramgoolam, <a href="http://arxiv.org/abs/1307.6490">Counting Tensor Model Observables and Branched Covers of the 2-Sphere</a>, arXiv preprint arXiv:1307.6490 [hep-th], 2013. %Y A232216 Column k=4 of A333733. %K A232216 nonn %O A232216 0,3 %A A232216 _N. J. A. Sloane_, Nov 22 2013 %E A232216 Name changed, a(0)=1 prepended and a(9)-a(20) from _Andrew Howroyd_, Apr 04 2020