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A268761 Number of n X 3 binary arrays with some element plus some horizontally, vertically, diagonally or antidiagonally adjacent neighbor totalling two exactly once. 1
2, 15, 56, 223, 762, 2607, 8500, 27411, 86622, 270955, 838224, 2573015, 7841538, 23759463, 71619436, 214933915, 642504870, 1914023267, 5684288136, 16834582623, 49732758858, 146587890015, 431177727396, 1265883329827, 3710027613934 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

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*(2 + 7*x - 8*x^2 + x^3) / (1 - 2*x - 3*x^2 + 2*x^3)^2. - Colin Barker, Jan 14 2019

EXAMPLE

Some solutions for n=4:

..1..0..1. .0..1..1. .1..0..0. .1..0..1. .0..1..0. .1..1..0. .0..0..0

..0..0..1. .0..0..0. .0..0..0. .0..0..0. .0..0..1. .0..0..0. .0..0..0

..0..0..0. .0..0..0. .1..0..1. .0..1..0. .0..0..0. .0..0..0. .1..0..1

..0..0..0. .0..0..0. .0..0..1. .0..0..1. .0..0..1. .0..1..0. .1..0..0

CROSSREFS

Column 3 of A268766.

Sequence in context: A056078 A142861 A305673 * A088979 A265909 A034571

Adjacent sequences: A268758 A268759 A268760 * A268762 A268763 A268764

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 13 2016

STATUS

approved

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Last modified November 28 05:56 EST 2022. Contains 358407 sequences. (Running on oeis4.)