A230970 Number of (n+2) X (1+2) 0..3 arrays x(i,j) with each element diagonally or antidiagonally next to at least one element with value (x(i,j)+1) mod 4, no adjacent elements equal, and upper left element zero.

0, 16, 64, 256, 1344, 7056, 34944, 173056, 866944, 4343056, 21706944, 108493056, 542506944, 2712743056, 13563506944, 67816493056, 339083506944, 1695422743056, 8477108506944, 42385516493056, 211927608506944, 1059638172743056

Offset

1,2

Links

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

Formula

Empirical: a(n) = 4*a(n-1) + 20*a(n-3) + 25*a(n-4).

Empirical g.f.: 16*x^2 / ((1 + x)*(1 - 5*x)*(1 + 5*x^2)). - Colin Barker, Sep 25 2018

Example

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

Crossrefs

Column 1 of A230977.

Sequence in context: A255661 A384784 A073718 * A352738 A061449 A168091

Adjacent sequences: A230967 A230968 A230969 * A230971 A230972 A230973

Keyword

nonn

Author

R. H. Hardin, Nov 02 2013

Status

approved