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 A228278 #14 Mar 16 2018 12:44:02 %S A228278 2,3,13,35,112,337,1034,3154,9637,29431,89895,274564,838609,2561372, %T A228278 7823242,23894643,72981777,222909351,680835436,2079486057,6351405998, %U A228278 19399196250,59251261117,180972030923,552745635451,1688259428536 %N A228278 Number of n X 3 binary arrays with top left value 1 and no two ones adjacent horizontally, vertically or nw-se diagonally. %C A228278 Column 3 of A228285. %H A228278 R. H. Hardin, <a href="/A228278/b228278.txt">Table of n, a(n) for n = 1..210</a> %F A228278 a(n) = a(n-1) + 5*a(n-2) + 4*a(n-3) - a(n-5). %F A228278 G.f.: x*(2 + x - x^3) / ((1 + x)*(1 - 2*x - 3*x^2 - x^3 + x^4)). - _Colin Barker_, Mar 16 2018 %e A228278 Some solutions for n=4: %e A228278 ..1..0..0....1..0..0....1..0..0....1..0..1....1..0..0....1..0..1....1..0..0 %e A228278 ..0..0..0....0..0..0....0..0..1....0..0..0....0..0..0....0..0..0....0..0..0 %e A228278 ..0..0..1....0..0..0....0..0..0....0..0..0....1..0..0....0..0..1....0..1..0 %e A228278 ..0..0..0....1..0..1....1..0..0....0..1..0....0..0..1....0..1..0....1..0..0 %Y A228278 See A228277-A228285, especially the latter. %K A228278 nonn %O A228278 1,1 %A A228278 _R. H. Hardin_, Aug 19 2013 %E A228278 Edited by _N. J. A. Sloane_, Aug 22 2013