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A268776
Number of n X 3 binary arrays with some element plus some horizontally, vertically, diagonally or antidiagonally adjacent neighbor totalling two no more than once.
1
7, 26, 91, 316, 1031, 3354, 10615, 33344, 103339, 317958, 970515, 2945172, 8888719, 26705714, 79909167, 238257768, 708129267, 2098664158, 6203795403, 18296271036, 53845375703, 158159174410, 463734769895, 1357486034320, 3967761581627
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 4*a(n-1) + 2*a(n-2) - 16*a(n-3) - a(n-4) + 12*a(n-5) - 4*a(n-6).
Empirical g.f.: x*(7 - 2*x - 27*x^2 + 12*x^3 + 8*x^4 - 4*x^5) / (1 - 2*x - 3*x^2 + 2*x^3)^2. - Colin Barker, Jan 15 2019
EXAMPLE
Some solutions for n=4:
..0..1..0. .0..0..0. .0..0..0. .0..0..0. .0..0..0. .0..0..0. .0..1..0
..0..1..0. .0..1..1. .1..0..0. .0..0..0. .0..0..1. .0..1..0. .0..1..0
..0..0..0. .0..0..0. .0..0..1. .0..0..1. .1..0..0. .0..0..0. .0..0..0
..0..1..0. .0..1..0. .0..1..0. .1..0..0. .1..0..0. .0..0..1. .1..0..0
CROSSREFS
Column 3 of A268781.
Sequence in context: A372611 A279761 A245750 * A050476 A026617 A240261
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 13 2016
STATUS
approved