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A221246 Number of 2 X n arrays of occupancy after each element moves to some horizontal, diagonal or antidiagonal neighbor. 1
0, 9, 50, 484, 3864, 32400, 267264, 2214144, 18316800, 151585344, 1254325824, 10379534400, 85889605824, 710729930304, 5881230244800, 48666696727104, 402712880117184, 3332415765326400, 27575464553486784, 228184686537228864 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 2 of A221245.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 9*a(n-1) - 54*a(n-3) + 36*a(n-4) for n>5.

Empirical g.f.: x^2*(9 - 31*x + 34*x^2 - 6*x^3) / ((1 - 9*x + 6*x^2)*(1 - 6*x^2)). - Colin Barker, Aug 04 2018

EXAMPLE

Some solutions for n=3:

  1 3 1   0 3 0   2 2 0   0 4 2   0 2 0   1 4 1   0 2 2

  0 1 0   0 1 2   0 2 0   0 0 0   1 2 1   0 0 0   0 2 0

CROSSREFS

Cf. A221245.

Sequence in context: A279972 A115366 A188210 * A002462 A210061 A034814

Adjacent sequences:  A221243 A221244 A221245 * A221247 A221248 A221249

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 06 2013

STATUS

approved

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Last modified March 23 18:13 EDT 2019. Contains 321433 sequences. (Running on oeis4.)