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A268887 Number of 2 X n binary arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two exactly once. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified September 24 14:33 EDT 2021. Contains 347643 sequences. (Running on oeis4.)