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 A301611 #4 Mar 24 2018 11:39:37 %S A301611 2,34,367,3816,40085,421025,4422826,46459647,488047397,5126802206, %T A301611 53855652961,565739028561,5942934438842,62428910463417, %U A301611 655798724558441,6888987247456952,72366937453302201,760194996499019669 %N A301611 Number of nX4 0..1 arrays with every element equal to 1, 2 or 3 horizontally or vertically adjacent elements, with upper left element zero. %C A301611 Column 4 of A301615. %H A301611 R. H. Hardin, <a href="/A301611/b301611.txt">Table of n, a(n) for n = 1..210</a> %F A301611 Empirical: a(n) = 7*a(n-1) +41*a(n-2) -12*a(n-3) -318*a(n-4) -262*a(n-5) +724*a(n-6) +1034*a(n-7) -1340*a(n-8) -3422*a(n-9) +4016*a(n-10) +12158*a(n-11) +6925*a(n-12) -17989*a(n-13) -30269*a(n-14) +7574*a(n-15) +1694*a(n-16) +8004*a(n-17) -672*a(n-18) +432*a(n-19) -864*a(n-20) for n>21 %e A301611 Some solutions for n=5 %e A301611 ..0..0..0..0. .0..1..1..0. .0..0..1..1. .0..0..1..1. .0..0..1..1 %e A301611 ..1..0..1..1. .0..1..0..0. .1..1..0..1. .1..1..1..1. .0..1..0..1 %e A301611 ..1..1..1..0. .0..0..0..0. .0..1..0..0. .1..0..0..1. .1..1..0..0 %e A301611 ..0..1..1..0. .1..1..1..0. .0..1..1..1. .0..0..1..0. .1..1..1..1 %e A301611 ..0..1..1..1. .0..0..1..0. .0..0..0..1. .0..1..1..0. .1..0..0..0 %Y A301611 Cf. A301615. %K A301611 nonn %O A301611 1,1 %A A301611 _R. H. Hardin_, Mar 24 2018