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 A268792 #8 Jan 15 2019 09:23:18 %S A268792 3,22,78,234,652,1714,4360,10820,26366,63346,150482,354196,827310, %T A268792 1919884,4430664,10175910,23272918,53029498,120435100,272714858, %U A268792 615904208,1387638220,3119557838,6999162874,15675003042,35046218020 %N A268792 Number of n X 2 0..2 arrays with some element plus some horizontally, vertically or antidiagonally adjacent neighbor totalling two exactly once. %H A268792 R. H. Hardin, <a href="/A268792/b268792.txt">Table of n, a(n) for n = 1..210</a> %F A268792 Empirical: a(n) = 2*a(n-1) + 3*a(n-2) - 2*a(n-3) - 6*a(n-4) - 4*a(n-5) - a(n-6) for n>7. %F A268792 Empirical g.f.: x*(3 + 16*x + 25*x^2 + 18*x^3 + 12*x^4 + 8*x^5 + 3*x^6) / (1 - x - 2*x^2 - x^3)^2. - _Colin Barker_, Jan 15 2019 %e A268792 Some solutions for n=4: %e A268792 ..2..1. .0..0. .1..2. .0..0. .0..2. .2..2. .2..0. .0..0. .0..1. .1..2 %e A268792 ..0..0. .1..1. .2..1. .0..1. .1..2. .1..2. .1..0. .0..1. .0..0. .2..2 %e A268792 ..0..0. .0..0. .1..0. .2..2. .2..2. .2..2. .0..0. .0..0. .0..1. .2..1 %e A268792 ..0..0. .0..0. .0..1. .2..1. .2..1. .1..1. .0..1. .1..2. .1..0. .2..1 %Y A268792 Column 2 of A268798. %K A268792 nonn %O A268792 1,1 %A A268792 _R. H. Hardin_, Feb 13 2016