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 A189604 Number of nX3 array permutations with each element not moving, or moving one space E, S or NW. 1

%I

%S 1,6,20,72,256,912,3248,11568,41200,146736,522608,1861296,6629104,

%T 23609904,84087920,299483568,1066626544,3798846768,13529793392,

%U 48187073712,171620807920,611236571184,2176951329392,7753327130544

%N Number of nX3 array permutations with each element not moving, or moving one space E, S or NW.

%C Column 3 of A189610.

%C Binomial transform of A006131 starting (1, 5, 9, 29, 65,...). - _Gary W. Adamson_, Feb 19 2014

%H R. H. Hardin, <a href="/A189604/b189604.txt">Table of n, a(n) for n = 1..200</a>

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

%F G.f.: (x+3*x^2)/(1-3*x-2*x^2) [From _Vladimir Kruchinin_, May 13 2011]

%e Some solutions for 4X3

%e ..4..5..1....0..5..1....0..1..2....0..1..2....4..0..1....0..1..2....4..1..2

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

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

%e ..9.10.11....9.10.11....9..7.10....6..9.11....6..9..8....9.10.11....9.10.11

%Y Cf. A006131.

%K nonn

%O 1,2

%A _R. H. Hardin_, Apr 24 2011

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Last modified June 15 22:19 EDT 2019. Contains 324145 sequences. (Running on oeis4.)