A231038 Number of 2 X n 0..2 arrays x(i,j) with each element horizontally, 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, 0, 0, 4, 0, 32, 80, 560, 2080, 10720, 46496, 220896, 998432, 4634272, 21207840, 97791904, 449099040, 2066934176, 9501790240, 43707407520, 200983135008, 924361443232, 4250915450400, 19549937082016, 89907588137248

Offset

1,4

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + 6*a(n-2) + 32*a(n-4) - 20*a(n-5) + 24*a(n-6) - 16*a(n-7).

Empirical g.f.: 4*x^4*(1 - 3*x + 2*x^2 - 4*x^3) / (1 - 3*x - 6*x^2 - 32*x^4 + 20*x^5 - 24*x^6 + 16*x^7). - Colin Barker, Sep 25 2018

Example

All solutions for n=4:
..0..2..2..0....0..2..1..0....0..1..1..0....0..1..2..0
..0..1..1..0....0..1..2..0....0..2..2..0....0..2..1..0

Crossrefs

Row 2 of A231037.

Sequence in context: A270293 A270900 A123016 * A271280 A271086 A271292

Adjacent sequences: A231035 A231036 A231037 * A231039 A231040 A231041

Keyword

nonn

Author

R. H. Hardin, Nov 03 2013

Status

approved