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A189604 Number of nX3 array permutations with each element not moving, or moving one space E, S or NW. 1
1, 6, 20, 72, 256, 912, 3248, 11568, 41200, 146736, 522608, 1861296, 6629104, 23609904, 84087920, 299483568, 1066626544, 3798846768, 13529793392, 48187073712, 171620807920, 611236571184, 2176951329392, 7753327130544 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 3 of A189610.

Binomial transform of A006131 starting (1, 5, 9, 29, 65,...). - Gary W. Adamson, Feb 19 2014

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n) = 3*a(n-1) +2*a(n-2).

G.f.: (x+3*x^2)/(1-3*x-2*x^2) [From Vladimir Kruchinin, May 13 2011]

EXAMPLE

Some solutions for 4X3

..4..5..1....0..5..1....0..1..2....0..1..2....4..0..1....0..1..2....4..1..2

..0..3..2....7..4..2....3..4..5....3..4..5....7..3..2....3..8..5....0..3..5

..6..7..8....3..6..8....6.11..8...10..7..8...10.11..5....6..4..7....6..7..8

..9.10.11....9.10.11....9..7.10....6..9.11....6..9..8....9.10.11....9.10.11

CROSSREFS

Cf. A006131.

Sequence in context: A075055 A146891 A235367 * A153372 A028402 A092760

Adjacent sequences:  A189601 A189602 A189603 * A189605 A189606 A189607

KEYWORD

nonn

AUTHOR

R. H. Hardin, Apr 24 2011

STATUS

approved

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Last modified May 26 19:44 EDT 2019. Contains 323597 sequences. (Running on oeis4.)