A268735 Number of n X 3 binary arrays with some 1 horizontally or vertically adjacent to some other 1 exactly once.

2, 15, 80, 396, 1788, 7831, 33170, 137868, 563486, 2275119, 9091772, 36031648, 141793168, 554669335, 2158604934, 8363066408, 32273565050, 124112115647, 475807505288, 1819019281732, 6936664653476, 26392068734023, 100206016839642

Offset

1,1

Links

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

Formula

Empirical: a(n) = 4*a(n-1) + 8*a(n-2) - 24*a(n-3) - 38*a(n-4) + 4*a(n-5) + 12*a(n-6) - a(n-8).

Empirical g.f.: x*(2 + 7*x + 4*x^2 + 4*x^3 - 7*x^5 + 2*x^6) / (1 - 2*x - 6*x^2 + x^4)^2. - Colin Barker, Jan 14 2019

Example

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

Crossrefs

Column 3 of A268740.

Sequence in context: A056079 A266622 A036239 * A215705 A368783 A301566

Adjacent sequences: A268732 A268733 A268734 * A268736 A268737 A268738

Keyword

nonn

Author

R. H. Hardin, Feb 12 2016

Status

approved