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 A172556 #19 Oct 13 2024 19:02:58 %S A172556 1,20,1860,297200,60871300,14367744720,3718394156400,1026608414145600, %T A172556 297348703692826500,89365729945562642000,27658131940039664137360, %U A172556 8766913970029589057611200,2834492178580299130305958000,931874436031756882451601080000,310768686646948895430510472680000 %N A172556 Number of 2*n X 6 binary arrays with row sums 3 and column sums n. %H A172556 Christoph Koutschan, <a href="/A172556/b172556.txt">Table of n, a(n) for n = 0..387</a> (terms n=1..49 from R. H. Hardin) %H A172556 Robert Dougherty-Bliss, Christoph Koutschan, Natalya Ter-Saakov, and Doron Zeilberger, <a href="https://arxiv.org/abs/2410.07435">The (Symbolic and Numeric) Computational Challenges of Counting 0-1 Balanced Matrices</a>, arXiv:2410.07435 [math.CO], 2024. %F A172556 (n+3) * (n+4)^5 * (33*n^2 + 176*n + 236) * a(n+4) = 2 * (n+3) * (2*n + 7) * (3201*n^6 + 61886*n^5 + 497179*n^4 + 2124170*n^3 + 5089654*n^2 + 6484024*n + 3431096) * a(n+3) + 16 * (2*n + 5) * (2*n + 7) * (2772*n^6 + 48048*n^5 + 344379*n^4 + 1307394*n^3 + 2775099*n^2 + 3125336*n + 1460132) * a(n+2) - 128 * (n+2) * (2*n + 3) * (2*n + 5) * (2*n + 7) * (7491*n^4 + 84898*n^3 + 351364*n^2 + 628997*n + 414370) * a(n+1) + 51200 * (n+1) * (n+2) * (2*n + 1) * (2*n + 3) * (2*n + 5) * (2*n + 7) * (33*n^2 + 242*n + 445) * a(n). - _Doron Zeilberger_ and _Christoph Koutschan_, Oct 13 2024 %Y A172556 Column k=3 of A376935. %K A172556 nonn %O A172556 0,2 %A A172556 _R. H. Hardin_, Feb 06 2010 %E A172556 a(0)=1 prepended by _Andrew Howroyd_, Oct 12 2024