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 A331710 #7 Jan 25 2020 20:55:32
%S A331710 1,3,45,1987,190379,30474159,7287577611,2436916655479,
%T A331710 1085776582252197,621663581843731535,444746638465623906738,
%U A331710 388773810523972862494769,407727415097448880517583006,505268334502886263575349570013,730406898110019766652845079212010
%N A331710 Number of nonnegative integer matrices with n columns and any number of distinct nonzero rows with column sums 3 and columns in nonincreasing lexicographic order.
%C A331710 The condition that the columns be in nonincreasing order is equivalent to considering nonequivalent matrices up to permutation of columns.
%H A331710 Andrew Howroyd, <a href="/A331710/b331710.txt">Table of n, a(n) for n = 0..100</a>
%F A331710 a(n) = (1/n!)*Sum_{k=0..n} abs(Stirling1(n, k)) * A331645(k).
%e A331710 The a(1) = 3 matrices are:
%e A331710 [2] [1] [3]
%e A331710 [1] [2]
%Y A331710 Row n=3 of A331572.
%Y A331710 Cf. A331645, A331709.
%K A331710 nonn
%O A331710 0,2
%A A331710 _Andrew Howroyd_, Jan 25 2020