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A278274 Number of n X 2 0..1 arrays with every element both equal and not equal to some elements at offset (-1,-1) (-1,0) (-1,1) (0,-1) (0,1) or (1,0), with upper left element zero. 1
0, 2, 5, 16, 49, 153, 476, 1483, 4619, 14388, 44817, 139601, 434844, 1354499, 4219139, 13142228, 40936825, 127514425, 397195644, 1237227707, 3853849915, 12004386164, 37392552993, 116474345313, 362806816604, 1130109689139, 3520187193395 (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) = 3*a(n-1) + a(n-2) - 2*a(n-3) for n>4.

Empirical g.f.: x^2*(1 - x)*(2 + x) / (1 - 3*x - x^2 + 2*x^3). - Colin Barker, Feb 09 2019

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Column 2 of A278280.

Sequence in context: A005497 A148381 A334293 * A148382 A148383 A148384

Adjacent sequences:  A278271 A278272 A278273 * A278275 A278276 A278277

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 16 2016

STATUS

approved

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Last modified January 24 08:21 EST 2021. Contains 340398 sequences. (Running on oeis4.)