A251122 Number of (n+1) X (2+1) 0..1 arrays with no 2 X 2 subblock having the sum of its diagonal elements greater than the maximum of its antidiagonal elements.

21, 40, 69, 117, 193, 315, 510, 823, 1326, 2136, 3442, 5550, 8955, 14458, 23355, 37743, 61015, 98661, 159564, 258097, 417516, 675450, 1092784, 1768032, 2860593, 4628380, 7488705, 12116793, 19605181, 31721631, 51326442, 83047675, 134373690

Offset: 1

Author

R. H. Hardin, Nov 30 2014

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 2 of A251128.

Formula

Empirical: a(n) = 4*a(n-1) - 5*a(n-2) + a(n-3) + 2*a(n-4) - a(n-5).

Empirical g.f.: x*(21 - 44*x + 14*x^2 + 20*x^3 - 12*x^4) / ((1 - x)^3*(1 - x - x^2)). - Colin Barker, Nov 25 2018