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 A303457 #4 Apr 24 2018 10:23:11 %S A303457 4,32,232,1690,12340,90112,658204,4807732,35118024,256519346, %T A303457 1873747524,13686804048,99975389852,730271188300,5334272943080, %U A303457 38964248230442,284614727917460,2078971032009920,15185864006789660,110925290484682724 %N A303457 Number of 3Xn 0..1 arrays with every element equal to 0, 1, 2, 3, 4 or 6 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A303457 Row 3 of A303456. %H A303457 R. H. Hardin, <a href="/A303457/b303457.txt">Table of n, a(n) for n = 1..210</a> %F A303457 Empirical: a(n) = 8*a(n-1) -40*a(n-3) +20*a(n-4) +8*a(n-5) -3*a(n-6) +32*a(n-7) for n>8 %e A303457 Some solutions for n=5 %e A303457 ..0..0..1..0..0. .0..0..0..1..0. .0..0..0..0..1. .0..1..0..0..0 %e A303457 ..0..0..0..1..0. .0..0..0..1..0. .0..0..1..0..1. .1..1..1..1..0 %e A303457 ..1..1..1..1..0. .0..0..0..0..0. .1..1..0..1..0. .1..0..0..0..1 %Y A303457 Cf. A303456. %K A303457 nonn %O A303457 1,1 %A A303457 _R. H. Hardin_, Apr 24 2018