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A296719 Number of n X 2 0..1 arrays with each 1 adjacent to 0, 2 or 4 king-move neighboring 1s. 1
3, 9, 21, 57, 153, 393, 1041, 2745, 7185, 18921, 49761, 130713, 343761, 903753, 2375553, 6245625, 16419249, 43163817, 113476065, 298319193, 784254225, 2061749001, 5420172609, 14249195961, 37460035185, 98479462761, 258894708897 (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) = a(n-1) + 2*a(n-2) + 6*a(n-3).

Empirical g.f.: 3*x*(1 + 2*x + 2*x^2) / (1 - x - 2*x^2 - 6*x^3).

EXAMPLE

Some solutions for n=5:

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

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

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

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

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

CROSSREFS

Column 2 of A296725.

Sequence in context: A191796 A007056 A026551 * A060578 A147078 A146416

Adjacent sequences:  A296716 A296717 A296718 * A296720 A296721 A296722

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 19 2017

STATUS

approved

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Last modified September 30 11:32 EDT 2020. Contains 337439 sequences. (Running on oeis4.)