A234381 Number of (1+2) X (n+2) 0..2 arrays with no increasing sequence of length 3 horizontally or diagonally downwards.

16584, 406416, 9995040, 245837376, 6045322368, 148657436928, 3655605662208, 89894348448768, 2210574247446528, 54359793423323136, 1336750972483608576, 32871779997322199040, 808343468249908543488, 19877815029157007523840

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 24*a(n-1) - 12*a(n-2) + 624*a(n-3) + 1056*a(n-4) - 8448*a(n-5) - 9216*a(n-6).

Empirical g.f.: 24*x*(691 + 350*x + 18336*x^2 + 20208*x^3 - 247936*x^4 - 259584*x^5) / (1 - 24*x + 12*x^2 - 624*x^3 - 1056*x^4 + 8448*x^5 + 9216*x^6). - Colin Barker, Oct 14 2018

Example

Some solutions for n=1:
  2 2 1   2 1 2   0 2 1   1 0 0   0 2 2   1 0 2   0 1 0
  1 0 1   2 0 2   0 0 0   0 0 0   1 2 0   0 2 1   0 1 2
  0 2 0   0 2 0   0 2 0   1 1 2   1 2 2   0 1 0   0 0 0

Crossrefs

Row 1 of A234380.

Sequence in context: A344242 A234374 A234380 * A236638 A250930 A210272

Adjacent sequences: A234378 A234379 A234380 * A234382 A234383 A234384

Keyword

nonn

Author

R. H. Hardin, Dec 25 2013

Status

approved