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A232336 Number of 2 X n 0..2 arrays with every 0 next to a 1 and every 1 next to a 2 horizontally or antidiagonally, with no adjacent elements equal. 1
1, 6, 18, 32, 82, 162, 388, 806, 1858, 3968, 8962, 19426, 43396, 94822, 210578, 462112, 1022994, 2250178, 4972804, 10951878, 24180994, 53291008, 117604738, 259275842, 572028164, 1261360966, 2782483346, 6136209184, 13535050578, 29850527586 (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) + 3*a(n-2) - a(n-3) + a(n-4) - a(n-5) for n>6.

Empirical g.f.: x*(1 + 5*x + 9*x^2 - 3*x^3 + x^4 - 3*x^5) / ((1 + x - x^2)*(1 - 2*x - x^3)). - Colin Barker, Oct 04 2018

EXAMPLE

Some solutions for n=7:

..2..0..1..0..2..1..0....2..1..2..1..0..2..1....1..2..1..0..2..0..1

..1..2..1..0..2..1..2....2..1..2..1..0..2..1....1..2..1..0..1..2..1

CROSSREFS

Row 2 of A232335.

Sequence in context: A256256 A280802 A124353 * A153126 A110671 A134078

Adjacent sequences:  A232333 A232334 A232335 * A232337 A232338 A232339

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 22 2013

STATUS

approved

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Last modified October 19 04:40 EDT 2019. Contains 328211 sequences. (Running on oeis4.)