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 A250669 #6 Jul 23 2025 12:39:48 %S A250669 104,520,2512,11736,53032,233300,1005121,4260728,17835379,73930174, %T A250669 304111433,1243471948,5060483311,20518170938,82950532885,334582615528, %U A250669 1347111707003,5416107760342,21751360774177,87278063198468 %N A250669 Number of (n+1)X(1+1) 0..3 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. %C A250669 Column 1 of A250676 %H A250669 R. H. Hardin, <a href="/A250669/b250669.txt">Table of n, a(n) for n = 1..210</a> %F A250669 Empirical: a(n) = 16*a(n-1) -106*a(n-2) +376*a(n-3) -769*a(n-4) +904*a(n-5) -564*a(n-6) +144*a(n-7) for n>11 %e A250669 Some solutions for n=4 %e A250669 ..2..1....2..0....0..2....2..0....0..0....0..0....1..1....1..0....2..1....0..1 %e A250669 ..0..3....1..2....1..1....1..1....0..2....0..1....0..2....0..1....0..3....0..3 %e A250669 ..2..1....1..2....1..1....0..2....1..1....1..3....1..3....0..1....0..3....0..3 %e A250669 ..3..0....2..1....2..2....0..2....2..2....2..2....2..2....0..3....3..0....2..1 %e A250669 ..0..3....2..2....1..3....1..1....3..1....2..3....2..2....2..1....0..3....1..3 %K A250669 nonn %O A250669 1,1 %A A250669 _R. H. Hardin_, Nov 26 2014