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 A268890 #4 Feb 15 2016 11:37:09 %S A268890 0,235,2418,31956,317966,3283890,31427480,299524050,2777161184, %T A268890 25505113994,231143340184,2077724593805,18526267129268, %U A268890 164165431218906,1446558738555296,12686251671077220,110791183092125102 %N A268890 Number of 5Xn binary arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two exactly once. %C A268890 Row 5 of A268886. %H A268890 R. H. Hardin, <a href="/A268890/b268890.txt">Table of n, a(n) for n = 1..210</a> %F A268890 Empirical: a(n) = 2*a(n-1) +97*a(n-2) +116*a(n-3) -2923*a(n-4) -10986*a(n-5) +4951*a(n-6) +72992*a(n-7) +36740*a(n-8) -223968*a(n-9) -159382*a(n-10) +423052*a(n-11) +256370*a(n-12) -539504*a(n-13) -176570*a(n-14) +450908*a(n-15) +6166*a(n-16) -217920*a(n-17) +57416*a(n-18) +45120*a(n-19) -25021*a(n-20) +562*a(n-21) +2089*a(n-22) -388*a(n-23) -31*a(n-24) +14*a(n-25) -a(n-26) %e A268890 Some solutions for n=4 %e A268890 ..1..1..0..1. .1..0..0..0. .1..0..1..1. .1..0..0..0. .1..0..1..0 %e A268890 ..0..1..0..1. .0..0..0..1. .1..0..0..0. .0..0..0..1. .1..0..0..0 %e A268890 ..0..1..0..0. .1..0..0..0. .1..0..0..0. .1..1..0..1. .0..0..1..1 %e A268890 ..0..0..0..1. .1..0..0..0. .0..0..0..0. .0..0..0..1. .1..0..0..1 %e A268890 ..0..1..0..0. .1..0..1..1. .0..0..0..1. .0..0..0..1. .0..0..0..0 %Y A268890 Cf. A268886. %K A268890 nonn %O A268890 1,2 %A A268890 _R. H. Hardin_, Feb 15 2016