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 A251262 #7 Nov 27 2018 11:37:20 %S A251262 26,114,480,2058,8812,37772,161906,694042,2975162,12753740,54671978, %T A251262 234364684,1004661088,4306723662,18461816670,79141059954,339257370296, %U A251262 1454309095546,6234249070708,26724622430876,114561583275826 %N A251262 Number of (n+1) X (2+1) 0..1 arrays with no 2 X 2 subblock having x11-x00 less than x10-x01. %H A251262 R. H. Hardin, <a href="/A251262/b251262.txt">Table of n, a(n) for n = 1..210</a> %F A251262 Empirical: a(n) = 5*a(n-1) - 2*a(n-2) - 5*a(n-3) + 2*a(n-4). %F A251262 Empirical g.f.: 2*x*(13 - 8*x - 19*x^2 + 8*x^3) / (1 - 5*x + 2*x^2 + 5*x^3 - 2*x^4). - _Colin Barker_, Nov 27 2018 %e A251262 Some solutions for n=4: %e A251262 ..0..1..0....1..1..1....1..1..1....0..0..0....0..1..0....1..0..1....0..1..1 %e A251262 ..1..0..1....0..1..1....0..1..1....0..0..0....0..0..1....0..1..1....1..1..1 %e A251262 ..0..1..1....0..0..0....0..0..0....1..1..1....0..1..0....0..1..1....0..0..1 %e A251262 ..0..0..0....0..0..0....0..0..1....0..1..1....0..0..1....0..1..1....0..0..1 %e A251262 ..1..1..1....0..1..1....0..1..1....1..1..1....1..1..0....1..0..0....0..1..1 %Y A251262 Column 2 of A251268. %K A251262 nonn %O A251262 1,1 %A A251262 _R. H. Hardin_, Dec 01 2014