A250753 Number of (n+1) X (6+1) 0..2 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nondecreasing x(i,j)+x(i-1,j) in the j direction.
402, 1305, 4182, 13149, 40722, 124785, 379662, 1149669, 3470442, 10454265, 31448742, 94518189, 283898562, 852383745, 2558527422, 7678334709, 23040509082, 69132537225, 207419631702, 622302935229, 1866996886002, 5601166818705
Offset: 1
Keywords
Examples
Some solutions for n=4: ..1..1..1..1..1..1..1....1..1..1..1..1..1..1....1..1..1..1..1..1..1 ..0..0..0..0..0..0..0....0..0..0..0..0..0..0....1..1..1..1..2..2..2 ..2..2..2..2..2..2..2....2..2..2..2..2..2..2....0..0..0..0..1..1..1 ..0..1..1..2..2..2..2....2..2..2..2..2..2..2....1..1..1..1..2..2..2 ..0..1..1..2..2..2..2....0..0..0..0..0..0..1....0..0..0..1..2..2..2
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Crossrefs
Column 6 of A250755.
Formula
Empirical: a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3); a(n) = (357*3^n - 168*2^n + 69)/2.
Empirical g.f.: 3*x*(134 - 369*x + 258*x^2) / ((1 - x)*(1 - 2*x)*(1 - 3*x)). - Colin Barker, Nov 17 2018