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 A284766 #6 Apr 05 2020 23:02:06 %S A284766 1,14,119,720,5637,38792,298003,2180148,16717575,125826436,966619242, %T A284766 7382318636,56924033734,438478307376,3394276530311,26291371821860, %U A284766 204232995801978,1588199807894658,12373790849896599,96512252060362420 %N A284766 Number of n X 3 0..1 arrays with the number of 1's horizontally or vertically adjacent to some 0 one less than the number of 0's adjacent to some 1. %C A284766 Column 3 of A284771. %H A284766 R. H. Hardin, <a href="/A284766/b284766.txt">Table of n, a(n) for n = 1..210</a> %e A284766 Some solutions for n=4 %e A284766 ..1..1..1. .1..0..1. .0..1..0. .1..0..0. .0..0..0. .1..0..1. .0..0..1 %e A284766 ..0..0..0. .1..0..0. .1..0..0. .1..0..0. .1..0..0. .0..0..0. .1..0..1 %e A284766 ..0..1..1. .0..0..1. .0..0..0. .0..1..0. .0..1..0. .0..0..0. .0..1..0 %e A284766 ..0..0..0. .0..1..1. .1..1..1. .0..0..1. .0..1..1. .1..1..1. .1..0..0 %Y A284766 Cf. A284771. %K A284766 nonn %O A284766 1,2 %A A284766 _R. H. Hardin_, Apr 02 2017