A231248 Number of 3 X n 0..3 arrays x(i,j) with each element horizontally, 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, 6, 78, 464, 3090, 22460, 162766, 1169472, 8396770, 60331460, 433549110, 3115381720, 22385974490, 160857679996, 1155868628526, 8305679220784, 59681777605042, 428852885779252, 3081590524869798, 22143258241832392

Offset

1,2

Links

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

Formula

Empirical: a(n) = 7*a(n-1) - 3*a(n-2) + 27*a(n-3) + 28*a(n-4) + 14*a(n-5) - 8*a(n-6) - 8*a(n-7) for n>8.

Empirical g.f.: 2*x^2*(3 + 18*x - 32*x^2 - 43*x^3 - 26*x^4 + 10*x^5 + 12*x^6) / (1 - 7*x + 3*x^2 - 27*x^3 - 28*x^4 - 14*x^5 + 8*x^6 + 8*x^7). - Colin Barker, Sep 28 2018

Example

Some solutions for n=4:
..0..1..0..1....0..3..2..1....0..3..2..1....0..1..2..1....0..3..0..3
..2..3..2..1....0..1..0..1....2..1..0..1....2..3..2..3....2..1..2..1
..0..1..0..3....2..3..2..1....0..3..2..3....0..1..0..1....0..1..0..3

Crossrefs

Row 3 of A231246.

Sequence in context: A134788 A167498 A250388 * A160240 A069669 A145359

Adjacent sequences: A231245 A231246 A231247 * A231249 A231250 A231251

Keyword

nonn

Author

R. H. Hardin, Nov 06 2013

Status

approved