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 A269070 #7 Jan 18 2019 15:00:33 %S A269070 7,27,123,537,2343,10167,43959,189465,814359,3491691,14937987, %T A269070 63778065,271799175,1156345287,4911870063,20834207313,88251723687, %U A269070 373358554971,1577691954507,6659543294313,28081651307943,118299768626103 %N A269070 Number of n X 3 binary arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two not more than once. %H A269070 R. H. Hardin, <a href="/A269070/b269070.txt">Table of n, a(n) for n = 1..210</a> %F A269070 Empirical: a(n) = 10*a(n-1) - 31*a(n-2) + 24*a(n-3) + 21*a(n-4) - 18*a(n-5) - 9*a(n-6). %F A269070 Empirical g.f.: x*(7 - 43*x + 70*x^2 - 24*x^3 - 9*x^4 - 9*x^5) / (1 - 5*x + 3*x^2 + 3*x^3)^2. - _Colin Barker_, Jan 18 2019 %e A269070 Some solutions for n=4: %e A269070 ..0..0..0. .0..0..1. .0..1..0. .1..0..1. .1..0..1. .1..0..0. .1..0..1 %e A269070 ..0..0..0. .0..1..0. .1..0..0. .0..0..0. .0..0..0. .1..0..1. .0..0..0 %e A269070 ..1..0..0. .0..0..0. .1..0..0. .1..0..0. .0..1..0. .0..0..0. .0..0..0 %e A269070 ..1..0..1. .1..0..1. .0..0..1. .0..0..1. .1..0..0. .0..0..0. .1..1..0 %Y A269070 Column 3 of A269075. %K A269070 nonn %O A269070 1,1 %A A269070 _R. H. Hardin_, Feb 19 2016