A251320 Number of (n+1) X (2+1) 0..1 arrays with every 2 X 2 subblock having one or two 1s.

28, 116, 474, 1982, 8218, 34288, 142600, 594236, 2473510, 10302766, 42897286, 178649320, 743905252, 3097889852, 12900178658, 53720031766, 223702349874, 931554901848, 3879218692624, 16154045069844, 67269408740158

Offset

1,1

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + 8*a(n-2) - 13*a(n-3) - a(n-4) + 2*a(n-5).

Empirical g.f.: 2*x*(14 + 16*x - 49*x^2 - 2*x^3 + 8*x^4) / ((1 + 2*x - x^2)*(1 - 5*x + 3*x^2 + 2*x^3)). - Colin Barker, Nov 28 2018

Example

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

Crossrefs

Column 2 of A251326.

Sequence in context: A042534 A042536 A042538 * A233372 A220755 A244079

Adjacent sequences: A251317 A251318 A251319 * A251321 A251322 A251323

Keyword

nonn

Author

R. H. Hardin, Dec 01 2014

Status

approved