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 A331648 #5 Jan 25 2020 02:24:07
%S A331648 1,4,16,91,546,5094,47306,561190,7098943,103345704,1622632638,
%T A331648 28216141886,526858348514,10659286804538,230286817182060,
%U A331648 5319206290975993,130370767029136518,3386434807625742926,92801587319328412310,2677967917777310591454,81124837170900250181072
%N A331648 Number of nonnegative integer matrices with distinct nonzero rows, total sum n and columns with equal sums.
%F A331648 a(n) = Sum_{d|n} A331568(d/n, d).
%e A331648 The a(2) = 4 matrices are:
%e A331648 [1 0] [0 1] [1 1] [2]
%e A331648 [0 1] [1 0]
%Y A331648 Cf. A331568.
%K A331648 nonn
%O A331648 1,2
%A A331648 _Andrew Howroyd_, Jan 24 2020