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 A331317 #10 Jan 24 2020 15:58:12
%S A331317 0,1,4,15,44,120,319,804,1960,4652,10782,24435,54329,118663,254969,
%T A331317 539825,1127247,2323811,4733634,9535025,19005218,37507726,73333405,
%U A331317 142112298,273092198,520612163,984943887,1849920530,3450475858,6393203485,11770416017,21538245911,39181212114
%N A331317 Number of nonnegative integer matrices with 2 distinct columns and any number of distinct nonzero rows with each column sum being n and rows in decreasing lexicographic order.
%C A331317 The condition that the rows be in decreasing order is equivalent to considering nonequivalent matrices with distinct rows up to permutation of rows.
%H A331317 Andrew Howroyd, <a href="/A331317/b331317.txt">Table of n, a(n) for n = 0..400</a>
%F A331317 a(n) = A219554(n) - A000009(n).
%o A331317 (PARI) a(n)={my(p=prod(i=0, n, prod(j=0, n, 1 + x^i*y^j + O(x*x^n) + O(y*y^n))), q=prod(i=1, n, 1 + x^i + O(x*x^n))); polcoef(polcoef(p,n), n)/2 - polcoef(q,n)}
%Y A331317 Column k=2 of A331160.
%Y A331317 Cf. A000009, A219554, A331197.
%K A331317 nonn
%O A331317 0,3
%A A331317 _Andrew Howroyd_, Jan 13 2020