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

1,1

Comments

Column 2 of A183819.

Links

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

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

Example

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

Crossrefs

Cf. A183819.

Sequence in context: A065116 A240410 A061250 * A222274 A061711 A316998

Adjacent sequences: A183810 A183811 A183812 * A183814 A183815 A183816

Keyword

nonn

Author

R. H. Hardin, Jan 07 2011

Status

approved