A183813 1/81 the number of (n+1) X 3 0..2 arrays with no 2 X 2 subblock being a reflection across the shared element pair of any horizontal or vertical neighbor.

8, 162, 3256, 65640, 1321860, 26630220, 536415300, 10805642100, 217666494900, 4384657426500, 88323978892500, 1779188631250500, 35839769985112500, 721952272492222500, 14542924237284172500, 292951012163242162500

Offset: 1

Author

R. H. Hardin, Jan 07 2011

Keywords

• nonn

Comments

Column 2 of A183819.

Examples

			Some solutions with upper left block zero for 5 X 3:
  0 0 0    0 0 0    0 0 1    0 0 2    0 0 1    0 0 0    0 0 2
  0 0 2    0 0 1    0 0 1    0 0 1    0 0 0    0 0 2    0 0 2
  0 1 0    0 2 0    0 1 2    2 1 1    0 2 2    1 1 0    0 2 2
  2 2 1    1 2 0    1 1 2    2 1 2    0 2 2    0 2 1    0 2 1
  1 0 1    1 0 2    1 1 1    0 2 1    0 1 0    1 2 2    2 0 0
		

Links

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

Crossrefs

Cf. A183819.

Formula

Empirical: a(n) = 15*a(n-1) + 120*a(n-2) - 330*a(n-3).

Empirical g.f.: 2*x*(4 + 21*x - 67*x^2) / (1 - 15*x - 120*x^2 + 330*x^3). - Colin Barker, Apr 04 2018