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 A301995 #4 Mar 30 2018 12:23:28 %S A301995 2,8,26,74,200,530,1394,3656,9578,25082,65672,171938,450146,1178504, %T A301995 3085370,8077610,21147464,55364786,144946898,379475912,993480842, %U A301995 2600966618,6809419016,17827290434,46672452290,122190066440,319897747034 %N A301995 Number of nX4 0..1 arrays with every element equal to 1, 2 or 4 horizontally or antidiagonally adjacent elements, with upper left element zero. %C A301995 Column 4 of A301999. %H A301995 R. H. Hardin, <a href="/A301995/b301995.txt">Table of n, a(n) for n = 1..210</a> %F A301995 Empirical: a(n) = 4*a(n-1) -4*a(n-2) +a(n-3) %e A301995 Some solutions for n=5 %e A301995 ..0..0..1..1. .0..0..1..0. .0..0..1..1. .0..0..1..1. .0..0..1..1 %e A301995 ..0..0..0..0. .0..1..0..0. .1..1..0..0. .0..1..0..1. .0..1..0..0 %e A301995 ..1..1..1..1. .1..1..0..0. .0..0..0..0. .1..0..1..1. .1..1..0..0 %e A301995 ..0..0..1..1. .1..1..0..0. .0..0..1..1. .0..0..1..0. .1..1..0..0 %e A301995 ..0..0..1..1. .1..1..1..1. .1..1..0..0. .1..1..0..0. .1..1..1..1 %Y A301995 Cf. A301999. %K A301995 nonn %O A301995 1,1 %A A301995 _R. H. Hardin_, Mar 30 2018