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 A268793 #4 Feb 13 2016 13:41:53 %S A268793 12,78,248,950,3384,11948,41248,140698,474472,1586038,5262024, %T A268793 17348096,56884272,185647624,603388088,1953997896,6307338900, %U A268793 20300666174,65169102416,208712267048,666993883320,2127375490930,6773070493400 %N A268793 Number of nX3 0..2 arrays with some element plus some horizontally, vertically or antidiagonally adjacent neighbor totalling two exactly once. %C A268793 Column 3 of A268798. %H A268793 R. H. Hardin, <a href="/A268793/b268793.txt">Table of n, a(n) for n = 1..210</a> %F A268793 Empirical: a(n) = 2*a(n-1) +9*a(n-2) -2*a(n-3) -33*a(n-4) -42*a(n-5) -14*a(n-6) +10*a(n-7) +8*a(n-8) -a(n-10) for n>12 %e A268793 Some solutions for n=4 %e A268793 ..2..2..1. .0..1..2. .0..0..0. .1..0..1. .1..0..0. .2..2..2. .2..1..0 %e A268793 ..1..2..2. .1..2..2. .1..0..1. .0..1..0. .0..0..1. .2..2..2. .1..0..1 %e A268793 ..1..2..1. .2..2..2. .0..1..0. .0..0..1. .0..0..2. .1..2..1. .0..0..0 %e A268793 ..2..2..2. .2..2..1. .0..0..0. .1..0..0. .0..1..2. .2..1..0. .0..1..0 %Y A268793 Cf. A268798. %K A268793 nonn %O A268793 1,1 %A A268793 _R. H. Hardin_, Feb 13 2016