A232336 Number of 2 X n 0..2 arrays with every 0 next to a 1 and every 1 next to a 2 horizontally or antidiagonally, with no adjacent elements equal.

1, 6, 18, 32, 82, 162, 388, 806, 1858, 3968, 8962, 19426, 43396, 94822, 210578, 462112, 1022994, 2250178, 4972804, 10951878, 24180994, 53291008, 117604738, 259275842, 572028164, 1261360966, 2782483346, 6136209184, 13535050578, 29850527586

Offset

1,2

Links

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

Formula

Empirical: a(n) = a(n-1) + 3*a(n-2) - a(n-3) + a(n-4) - a(n-5) for n>6.

Empirical g.f.: x*(1 + 5*x + 9*x^2 - 3*x^3 + x^4 - 3*x^5) / ((1 + x - x^2)*(1 - 2*x - x^3)). - Colin Barker, Oct 04 2018

Example

Some solutions for n=7:
..2..0..1..0..2..1..0....2..1..2..1..0..2..1....1..2..1..0..2..0..1
..1..2..1..0..2..1..2....2..1..2..1..0..2..1....1..2..1..0..1..2..1

Crossrefs

Row 2 of A232335.

Sequence in context: A344596 A280802 A124353 * A153126 A110671 A134078

Adjacent sequences: A232333 A232334 A232335 * A232337 A232338 A232339

Keyword

nonn

Author

R. H. Hardin, Nov 22 2013

Status

approved