A251311 Number of (n+1) X (2+1) 0..1 arrays with no 2 X 2 subblock having the maximum of its diagonal elements greater than the absolute difference of its antidiagonal elements.

25, 79, 238, 720, 2199, 6717, 20484, 62464, 190542, 581259, 1773061, 5408458, 16497878, 50325018, 153510819, 468267241, 1428396280, 4357161996, 13291031298, 40542790911, 123671208989, 377245070870, 1150743527834, 3510213300150

Offset

1,1

Links

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

Formula

Empirical: a(n) = 5*a(n-1) - 9*a(n-2) + 13*a(n-3) - 13*a(n-4) + 6*a(n-5) - 2*a(n-6).

Empirical g.f.: x*(25 - 46*x + 68*x^2 - 84*x^3 + 39*x^4 - 15*x^5) / (1 - 5*x + 9*x^2 - 13*x^3 + 13*x^4 - 6*x^5 + 2*x^6). - Colin Barker, Nov 28 2018

Example

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

Crossrefs

Column 2 of A251317.

Sequence in context: A033658 A080699 A134153 * A223181 A016814 A280343

Adjacent sequences: A251308 A251309 A251310 * A251312 A251313 A251314

Keyword

nonn

Author

R. H. Hardin, Dec 01 2014

Status

approved