A268887 Number of 2 X n binary arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two exactly once.

0, 5, 14, 54, 158, 475, 1340, 3740, 10204, 27521, 73354, 193842, 508346, 1324791, 3433720, 8858104, 22757432, 58253885, 148634502, 378142446, 959527766, 2429034323, 6135877428, 15469187604, 38929330452, 97806402617, 245354321666

Offset

1,2

Links

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

Formula

Empirical: a(n) = 2*a(n-1) + 5*a(n-2) - 4*a(n-3) - 11*a(n-4) - 6*a(n-5) - a(n-6).

Empirical g.f.: x^2*(5 + 4*x + x^2) / ((1 + x)^2*(1 - 2*x - x^2)^2). - Colin Barker, Jan 15 2019

Example

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

Crossrefs

Row 2 of A268886.

Sequence in context: A005504 A146746 A073541 * A055488 A177049 A127922

Adjacent sequences: A268884 A268885 A268886 * A268888 A268889 A268890

Keyword

nonn

Author

R. H. Hardin, Feb 15 2016

Status

approved