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 A331391 #8 Jan 15 2020 18:41:57
%S A331391 1,2,2,4,2,14,2,76,31,801,2,12797,2,233247,28480,5560377,2,160866915,
%T A331391 2,5351339038,193927186,208746406130,2,9342273087807,5289613,
%U A331391 470405726166256,4946464287635,26636935297440055,2,1679266767908385729,2,116818412262277969513
%N A331391 Number of binary matrices with a total of n ones, distinct columns each with the same number of ones and nonzero rows in nonincreasing lexicographic order.
%C A331391 The condition that the rows be in nonincreasing order is equivalent to considering nonequivalent matrices up to permutation of rows.
%F A331391 a(n) = Sum{d|n} A331126(n/d, d).
%F A331391 a(p) = 2 for prime p.
%e A331391 The a(4) = 4 matrices are:
%e A331391 [1 0 0 0] [1] [1 0] [1 1]
%e A331391 [0 1 0 0] [1] [1 0] [1 0]
%e A331391 [0 0 1 0] [1] [0 1] [0 1]
%e A331391 [0 0 0 1] [1] [0 1]
%Y A331391 Cf. A331126.
%K A331391 nonn
%O A331391 1,2
%A A331391 _Andrew Howroyd_, Jan 15 2020