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 A331712 #4 Jan 25 2020 20:55:52 %S A331712 1,4,59,1987,73567,2451082,75511809,2339355873,69675164655, %T A331712 1979830442230,54476566524395,1451352437084341,37417988223257669, %U A331712 936855055418767566,22833066207602691971,542259452455606556087,12569324678636155802527,284784345516796080566156,6313245421004111720679497 %N A331712 Number of nonnegative integer matrices with 3 columns and any number of distinct nonzero rows with column sums n and columns in nonincreasing lexicographic order. %C A331712 The condition that the columns be in nonincreasing order is equivalent to considering nonequivalent matrices up to permutation of columns. %e A331712 The a(1) = 4 matrices are: %e A331712 [1 0 0] [1 1 0] [1 0 0] [1 1 1] %e A331712 [0 1 0] [0 0 1] [0 1 1] %e A331712 [0 0 1] %Y A331712 Column k=3 of A331572. %Y A331712 Cf. A331711. %K A331712 nonn %O A331712 0,2 %A A331712 _Andrew Howroyd_, Jan 25 2020