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 A058408 #6 May 10 2013 12:44:33 %S A058408 1,4,26,129,546,2010,6615,19650,53790,137035,328262,745078,1613072, %T A058408 3348198,6693822,12937656,24253200,44219610,78604130,136511100, %U A058408 232054284 %N A058408 Number of 3 X n nonnegative integer matrices with all column sums 4, up to row and column permutation. %C A058408 Number of 3 X n nonnegative integer matrices with all column sums equal to m, up to row and column permutation, is coefficient of x^n in expansion of 1 / 6 * (1 / (1 - x)^C(m + 2,2) + 3 / (1 - x)^floor((m + 2) / 2) / (1 - x^2)^(C(m + 2,2) - floor((m + 2) / 2)) / 2 + 2 / (1 - x)^(C(m + 2,2) - 3 * floor(C(m + 2,2) / 3)) / (1 - x^3)^floor(C(m + 2,2) / 3)). %H A058408 <a href="/A058407/a058407.pdf">Number of m x l nonnegative integer matrices with all column sums equal to n, up to row and column permutation</a> %F A058408 G.f.: 1/6*(1/(1-x)^15+3/(1-x)^3/(1-x^2)^6+2/(1-x^3)^5). %Y A058408 Cf. A050531, A058389, A058407. %K A058408 easy,nonn %O A058408 0,2 %A A058408 _Vladeta Jovovic_, Nov 25 2000