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A278088 Number of n X 2 0..1 arrays with every element both equal and not equal to some elements at offset (-1,0) (-1,1) (0,-1) (0,1) or (1,0), with upper left element zero. 1
0, 2, 3, 10, 27, 76, 214, 599, 1683, 4721, 13250, 37183, 104346, 292828, 821761, 2306111, 6471639, 18161366, 50966255, 143026636, 401375754, 1126381063, 3160963987, 8870615501, 24893614638, 69858968603, 196045273658, 550161991984 (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) = a(n-1) + 4*a(n-2) + 3*a(n-3) for n>5.

Empirical g.f.: x^2*(2 + x - x^2 - x^3) / (1 - x - 4*x^2 - 3*x^3). - Colin Barker, Feb 07 2019

EXAMPLE

All solutions for n=4:

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

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

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

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

CROSSREFS

Column 2 of A278094.

Sequence in context: A211208 A303836 A238937 * A052929 A151415 A134588

Adjacent sequences:  A278085 A278086 A278087 * A278089 A278090 A278091

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 11 2016

STATUS

approved

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Last modified August 7 15:30 EDT 2020. Contains 336276 sequences. (Running on oeis4.)