A230813 - OEIS

A230813

Number of n X 2 0..2 arrays x(i,j) with each element horizontally or vertically 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, 0, 2, 0, 2, 12, 18, 56, 170, 420, 1162, 3200, 8562, 23292, 63298, 171336, 464890, 1261140, 3419322, 9274000, 25152322, 68211372, 184993778, 501712216, 1360654410, 3690150660, 10007829482, 27141578400, 73608971282, 199630236252

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

COMMENTS

Column 2 of A230819.

LINKS

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

FORMULA

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

Empirical g.f.: 2*x^3*(1 - 2*x) / (1 - 2*x - x^2 - 4*x^3 + 4*x^4). - Colin Barker, Mar 17 2018

EXAMPLE

All solutions for n=5:

..0..1....0..2

..2..2....1..1

..1..0....2..0

..2..2....1..1

..0..1....0..2

CROSSREFS

Cf. A230819.

Sequence in context: A107094 A122496 A335756 * A367074 A177113 A347010

Adjacent sequences: A230810 A230811 A230812 * A230814 A230815 A230816

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 30 2013

STATUS

approved