A221246 Number of 2 X n arrays of occupancy after each element moves to some horizontal, diagonal or antidiagonal neighbor.

0, 9, 50, 484, 3864, 32400, 267264, 2214144, 18316800, 151585344, 1254325824, 10379534400, 85889605824, 710729930304, 5881230244800, 48666696727104, 402712880117184, 3332415765326400, 27575464553486784, 228184686537228864

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: A188210 A308646 A338510 * A002462 A210061 A034814

Adjacent sequences: A221243 A221244 A221245 * A221247 A221248 A221249

Keyword

nonn

Author

R. H. Hardin, Jan 06 2013

Status

approved