A251081 Number of (n+1) X (1+1) 0..2 arrays with no 2 X 2 subblock having the sum of its diagonal elements greater than the absolute difference of its antidiagonal elements.

27, 83, 192, 420, 872, 1782, 3593, 7215, 14443, 28891, 57762, 115486, 230898, 461692, 923231, 1846265, 3692269, 7384217, 14768032, 29535584, 59070588, 118140498, 236280197, 472559475, 945117887, 1890234567, 3780467758, 7560933970

Offset

1,1

Links

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

Formula

Empirical: a(n) = 5*a(n-1) - 8*a(n-2) + 2*a(n-3) + 7*a(n-4) - 7*a(n-5) + 2*a(n-6) for n>7.

Empirical g.f.: x*(27 - 52*x - 7*x^2 + 70*x^3 - 47*x^4 + 6*x^5 + 2*x^6) / ((1 - x)^4*(1 + x)*(1 - 2*x)). - Colin Barker, Nov 24 2018

Example

Some solutions for n=4:
..1..2....0..1....1..2....2..2....2..2....2..2....1..2....0..2....1..2....0..2
..0..1....0..0....0..0....0..0....0..0....0..0....0..1....0..2....0..0....0..0
..0..1....2..2....1..1....1..1....1..0....2..2....0..0....1..1....0..0....2..2
..1..0....0..0....0..0....0..0....2..0....0..0....0..0....0..0....0..0....0..0
..1..0....1..0....2..2....1..1....2..0....2..2....0..0....1..0....0..0....1..0

Crossrefs

Column 1 of A251088.

Sequence in context: A042438 A251088 A044981 * A161340 A043182 A039359

Adjacent sequences: A251078 A251079 A251080 * A251082 A251083 A251084

Keyword

nonn

Author

R. H. Hardin, Nov 29 2014

Status

approved