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

1,1

Links

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

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

Example

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

Crossrefs

Column 2 of A251128.

Sequence in context: A339004 A270667 A020220 * A084856 A070666 A320775

Adjacent sequences: A251119 A251120 A251121 * A251123 A251124 A251125

Keyword

nonn

Author

R. H. Hardin, Nov 30 2014

Status

approved