A277939 Number of n X 2 0..2 arrays with every element plus 1 mod 3 equal to some element at offset (-1,0) (-1,1) (0,-1) (0,1) or (1,0), with upper left element zero.

0, 3, 14, 74, 377, 1932, 9888, 50619, 259118, 1326434, 6790049, 34758444, 177929400, 910825347, 4662539246, 23867662778, 122179202441, 625438596492, 3201636859344, 16389264488331, 83897082108014, 429471401309714

Offset

1,2

Links

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

Formula

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

Empirical g.f.: x^2*(3 + 2*x) / ((1 + x)*(1 - 5*x - x^2 + 2*x^3)). - Colin Barker, Feb 06 2019

Example

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

Crossrefs

Column 2 of A277945.

Sequence in context: A307443 A213228 A306455 * A210346 A074549 A245246

Adjacent sequences: A277936 A277937 A277938 * A277940 A277941 A277942

Keyword

nonn

Author

R. H. Hardin, Nov 05 2016

Status

approved