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 A331196 #9 Jan 24 2020 15:52:57
%S A331196 1,3,28,599,23243,1440532,131530132,16720208200,2837752812927,
%T A331196 622570020892599,172077041175850521,58679982298020226625,
%U A331196 24262822372018694983540,11986886218243164848742812,6987708088810202717378639087,4754544525981425409034078100189
%N A331196 Number of nonnegative integer matrices with n distinct columns and any number of nonzero rows with each column sum being 3 and rows in nonincreasing lexicographic order.
%C A331196 The condition that the rows be in nonincreasing order is equivalent to considering nonequivalent matrices up to permutation of rows.
%H A331196 Andrew Howroyd, <a href="/A331196/b331196.txt">Table of n, a(n) for n = 0..100</a>
%F A331196 a(n) = Sum_{k=0..n} Stirling1(n,k)*A322487(k).
%e A331196 The a(2) = 28 matrices include 6 with 2 rows, 10 with 3 rows, 8 with 4 rows, 3 with 5 rows and 1 with 6 rows. The 16 with 2 or 3 rows are:
%e A331196 [3 2] [3 1] [3 0] [2 3] [2 1] [2 0] [3 1] [3 0]
%e A331196 [0 1] [0 2] [0 3] [1 0] [1 2] [1 3] [0 1] [0 2]
%e A331196 [0 1] [0 1]
%e A331196 .
%e A331196 [2 2] [2 1] [2 1] [2 0] [2 0] [2 0] [1 3] [1 2]
%e A331196 [1 0] [1 1] [1 0] [1 2] [1 1] [1 0] [1 0] [1 1]
%e A331196 [0 1] [0 1] [0 2] [0 1] [0 2] [0 3] [1 0] [1 0]
%Y A331196 Row n=3 of A331161.
%Y A331196 Cf. A322487.
%K A331196 nonn
%O A331196 0,2
%A A331196 _Andrew Howroyd_, Jan 11 2020