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 A331643 #4 Jan 25 2020 00:58:02
%S A331643 1,3,13,81,541,4803,47293,552009,7088365,102697083,1622632573,
%T A331643 28141672449,526858348381,10648798871763,230283520498573,
%U A331643 5317134540336849,130370767029135901,3385908728450965323,92801587319328411133,2677804893723072559401,81124826179976677328845
%N A331643 Number of binary matrices with distinct nonzero rows, a total of n ones and each column with the same number of ones.
%F A331643 a(n) = Sum_{d|n} A331567(n/d, d).
%e A331643 The a(2) = 3 matrices are:
%e A331643 [1 0] [0 1] [1 1]
%e A331643 [0 1] [1 0]
%Y A331643 Cf. A331567.
%K A331643 nonn
%O A331643 1,2
%A A331643 _Andrew Howroyd_, Jan 24 2020