A230920 Number of n X 2 0..2 arrays x(i,j) with each element horizontally, vertically, diagonally or antidiagonally next to at least one element with value (x(i,j)+1) mod 3 and at least one element with value (x(i,j)-1) mod 3, and upper left element zero.

0, 12, 54, 432, 3108, 22428, 162504, 1175592, 8507376, 61562808, 445491480, 3223753560, 23328341064, 168813022728, 1221597213768, 8839956302856, 63969389202792, 462907576993032, 3349780692313320, 24240326242963080

Offset

1,2

Links

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

Formula

Empirical: a(n) = 5*a(n-1) + 14*a(n-2) + 16*a(n-3) - 2*a(n-4) + 4*a(n-5).

Empirical g.f.: 6*x^2*(1 - x)*(2 + x) / (1 - 5*x - 14*x^2 - 16*x^3 + 2*x^4 - 4*x^5). - Colin Barker, Sep 23 2018

Example

Some solutions for n=3:
..0..1....0..0....0..2....0..1....0..0....0..0....0..1....0..1....0..2....0..1
..1..2....2..1....1..2....1..2....1..2....1..2....2..2....2..0....1..0....2..1
..0..1....0..1....0..1....0..2....0..0....0..1....1..0....0..1....0..2....0..2

Crossrefs

Column 2 of A230926.

Sequence in context: A126399 A137938 A009726 * A190948 A275249 A143856

Adjacent sequences: A230917 A230918 A230919 * A230921 A230922 A230923

Keyword

nonn

Author

R. H. Hardin, Nov 01 2013

Status

approved