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 A301947 #4 Mar 29 2018 12:43:10 %S A301947 2,16,123,947,7326,56710,439078,3399722,26323903,203825456,1578217598, %T A301947 12220118582,94620225492,732643232114,5672847473255,43924787764759, %U A301947 340109088005893,2633460459021237,20390851741033347,157886112662767667 %N A301947 Number of nX4 0..1 arrays with every element equal to 1, 2 or 3 horizontally or antidiagonally adjacent elements, with upper left element zero. %C A301947 Column 4 of A301951. %H A301947 R. H. Hardin, <a href="/A301947/b301947.txt">Table of n, a(n) for n = 1..210</a> %F A301947 Empirical: a(n) = 9*a(n-1) -8*a(n-2) -14*a(n-3) +4*a(n-4) +4*a(n-5) -a(n-6) %e A301947 Some solutions for n=5 %e A301947 ..0..0..1..0. .0..0..1..1. .0..0..1..1. .0..0..0..0. .0..0..0..0 %e A301947 ..0..1..0..1. .0..0..1..1. .1..1..0..1. .0..0..1..1. .0..1..0..1 %e A301947 ..0..0..1..1. .0..0..0..1. .1..0..1..1. .0..1..1..1. .1..0..1..1 %e A301947 ..0..1..0..0. .1..1..1..0. .0..0..0..1. .1..0..1..0. .0..0..1..0 %e A301947 ..0..0..0..0. .1..1..0..0. .1..1..1..1. .0..1..0..0. .0..0..0..0 %Y A301947 Cf. A301951. %K A301947 nonn %O A301947 1,1 %A A301947 _R. H. Hardin_, Mar 29 2018