A186876 Number of (n+2) X 6 0..3 arrays with every 3 X 3 subblock commuting with each horizontal and vertical neighbor 3 X 3 subblock.

46583, 6829, 20152, 79096, 100600, 108640, 121144, 148048, 208576, 364504, 628144, 1130851, 1957270, 3187537, 5316589, 8884561, 14454997, 24229909, 40800838, 67069960, 112339666, 188701339, 310868899, 519362947, 870845683, 1438553446

Offset

1,1

Comments

Column 4 of A186881.

Links

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

Formula

Empirical: a(n) = 2*a(n-1) - a(n-2) + 3*a(n-3) - 6*a(n-4) + 3*a(n-5) + 3*a(n-6) - 3*a(n-7) for n>12.

Empirical g.f.: x*(46583 - 86337*x + 53077*x^2 - 94128*x^3 + 221571*x^4 - 172695*x^5 - 272148*x^6 + 245982*x^7 + 34047*x^8 - 94824*x^9 + 114075*x^11) / ((1 - x)*(1 - x - 3*x^3 + 3*x^4 - 3*x^6)). - Colin Barker, Apr 20 2018

Example

Some solutions for 4 X 6:
..0..1..0..0..0..0....0..0..0..0..0..1....0..0..0..0..0..3....0..0..0..0..2..0
..0..0..1..0..0..0....0..0..0..0..0..0....0..0..0..0..0..1....0..0..0..0..0..0
..3..0..0..1..0..0....0..0..0..0..0..0....3..0..0..0..0..0....1..0..0..0..0..0
..0..3..0..0..1..0....2..2..0..0..0..0....1..0..0..0..0..0....1..1..0..0..0..2

Crossrefs

Cf. A186881.

Sequence in context: A175170 A204495 A157527 * A103950 A057068 A223510

Adjacent sequences: A186873 A186874 A186875 * A186877 A186878 A186879

Keyword

nonn

Author

R. H. Hardin, Feb 28 2011

Status

approved