A278015 Number of 2 X n 0..2 arrays with every element plus 1 mod 3 equal to some element at offset (-1,-1) (-1,0) (-1,1) (0,-1) (0,1) or (1,0), with upper left element zero.

0, 6, 28, 168, 960, 5530, 31808, 183000, 1052800, 6056806, 34845028, 200464768, 1153281360, 6634871130, 38170663608, 219597266000, 1263351345600, 7268107893606, 41813698570028, 240555783389368, 1383926485841760

Offset

1,2

Links

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

Formula

Empirical: a(n) = 6*a(n-1) - 8*a(n-3) - a(n-4).

Empirical g.f.: 2*x^2*(3 - 4*x) / ((1 + x)*(1 - 7*x + 7*x^2 + x^3)). - Colin Barker, Feb 07 2019

Example

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

Crossrefs

Row 2 of A278014.

Sequence in context: A045722 A047129 A173081 * A338810 A345002 A169723

Adjacent sequences: A278012 A278013 A278014 * A278016 A278017 A278018

Keyword

nonn

Author

R. H. Hardin, Nov 08 2016

Status

approved