A232935 - OEIS

A232935

Number of n X 2 0..2 arrays with no element x(i,j) adjacent to value 2-x(i,j) horizontally, vertically or antidiagonally.

6, 12, 26, 56, 120, 258, 554, 1190, 2556, 5490, 11792, 25328, 54402, 116850, 250982, 539084, 1157898, 2487048, 5341928, 11473922, 24644826, 52934598, 113698172, 244212194, 524543136, 1126665696, 2419964162, 5197838690, 11164432710

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

OFFSET

1,1

LINKS

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

FORMULA

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

Empirical g.f.: 2*x*(3 + 3*x + x^2) / (1 - x - 2*x^2 - x^3). - Colin Barker, Oct 06 2018

EXAMPLE

Some solutions for n=5:

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

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

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

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

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

CROSSREFS

Column 2 of A232941.

Sequence in context: A177282 A283139 A242843 * A200079 A352091 A180509

Adjacent sequences: A232932 A232933 A232934 * A232936 A232937 A232938

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 02 2013

STATUS

approved