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 A250764 #7 Nov 18 2018 09:00:25 %S A250764 35,62,114,216,418,820,1622,3224,6426,12828,25630,51232,102434,204836, %T A250764 409638,819240,1638442,3276844,6553646,13107248,26214450,52428852, %U A250764 104857654,209715256,419430458,838860860,1677721662,3355443264 %N A250764 Number of (n+1) X (3+1) 0..1 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nondecreasing absolute value of x(i,j)-x(i-1,j) in the j direction. %H A250764 R. H. Hardin, <a href="/A250764/b250764.txt">Table of n, a(n) for n = 1..210</a> %F A250764 Empirical: a(n) = 4*a(n-1) - 5*a(n-2) + 2*a(n-3); a(n) = 25*2^(n-1) + 2*n + 8. %F A250764 Empirical g.f.: x*(35 - 78*x + 41*x^2) / ((1 - x)^2*(1 - 2*x)). - _Colin Barker_, Nov 18 2018 %e A250764 Some solutions for n=4: %e A250764 ..0..1..0..1....0..0..0..0....0..0..0..0....1..1..1..0....0..0..0..0 %e A250764 ..0..1..0..1....0..1..1..1....0..0..0..0....1..1..1..0....0..0..0..0 %e A250764 ..0..1..0..1....0..1..1..1....1..1..1..1....1..1..1..0....0..0..0..0 %e A250764 ..0..1..0..1....0..1..1..1....0..0..0..0....1..1..1..1....0..0..0..1 %e A250764 ..0..1..0..1....0..1..1..1....0..0..0..0....1..1..1..1....0..0..0..1 %Y A250764 Column 3 of A250769. %K A250764 nonn %O A250764 1,1 %A A250764 _R. H. Hardin_, Nov 27 2014