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

Author

R. H. Hardin, Jan 06 2013

Keywords

• nonn

Comments

Row 2 of A221245.

Examples

			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
		

Links

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

Crossrefs

Cf. A221245.

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