A268906 Number of 3 X n 0..2 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two exactly once.

0, 240, 1584, 9720, 54936, 299088, 1585800, 8244288, 42216696, 213602256, 1070280936, 5319700704, 26262038232, 128900271600, 629516497608, 3061019061504, 14827169463480, 71576870716944, 344483107968168

Offset

1,2

Links

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

Formula

Empirical: a(n) = 10*a(n-1) - 29*a(n-2) + 20*a(n-3) - 4*a(n-4) for n>6.

Empirical g.f.: 24*x^2*(10 - 34*x + 35*x^2 - 47*x^3 + 37*x^4) / (1 - 5*x + 2*x^2)^2. - Colin Barker, Jan 16 2019

Example

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

Crossrefs

Row 3 of A268904.

Sequence in context: A235205 A233878 A157766 * A234763 A268796 A290655

Adjacent sequences: A268903 A268904 A268905 * A268907 A268908 A268909

Keyword

nonn

Author

R. H. Hardin, Feb 15 2016

Status

approved