A231081 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, 2, 14, 40, 356, 1840, 10128, 60808, 337016, 1932520, 11047240, 62712776, 358084712, 2039935624, 11622103656, 66251217992, 377502949416, 2151360049288, 12260476416616, 69868714030792, 398172491295656, 2269109338791176

Offset

1,2

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + 12*a(n-2) + 30*a(n-3) - 64*a(n-4) + 16*a(n-5).

Empirical g.f.: x*2*(1 + 4*x - 13*x^2 + 4*x^3) / (1 - 3*x - 12*x^2 - 30*x^3 + 64*x^4 - 16*x^5). - Colin Barker, Sep 26 2018

Example

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

Crossrefs

Row 2 of A231080.

Sequence in context: A290124 A192349 A230801 * A364218 A152670 A109137

Adjacent sequences: A231078 A231079 A231080 * A231082 A231083 A231084

Keyword

nonn

Author

R. H. Hardin, Nov 03 2013

Status

approved