A186133 Number of (n+1) X 2 0..2 arrays with no 2 X 2 subblock trace equal to any horizontal or vertical neighbor 2 X 2 subblock trace.

81, 558, 3888, 27000, 187704, 1304424, 9066168, 63009576, 437922936, 3043586664, 21153140280, 147015651240, 1021768400376, 7101356197608, 49354885831608, 343019647846440, 2384008752240504, 16569015064994664, 115155726797070648

Offset

1,1

Comments

Column 1 of A186141.

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + 24*a(n-2) + 24*a(n-3).

Empirical g.f.: 9*x*(9 + 35*x + 30*x^2) / (1 - 3*x - 24*x^2 - 24*x^3). - Colin Barker, Feb 28 2018

Example

Some solutions for 3 X 2:
..1..1....2..2....1..2....0..2....2..2....2..0....2..1....2..2....1..2....1..1
..2..1....2..0....0..2....0..2....0..2....2..0....2..0....2..1....2..1....2..2
..2..1....2..1....2..1....0..0....1..1....2..1....0..1....2..2....1..2....0..0

Crossrefs

Cf. A186141.

Sequence in context: A253482 A186141 A185771 * A209506 A139156 A237035

Adjacent sequences: A186130 A186131 A186132 * A186134 A186135 A186136

Keyword

nonn

Author

R. H. Hardin, Feb 13 2011

Status

approved