A230245 Number of n X 2 0..3 arrays x(i,j) with each element horizontally or vertically next to at least one element with value (x(i,j)+1) mod 4, and upper left element zero.

0, 2, 6, 26, 118, 522, 2310, 10234, 45334, 200810, 889510, 3940186, 17453494, 77312202, 342463046, 1516978362, 6719625302, 29765331754, 131848865766, 584039296026, 2587067376886, 11459704266634, 50762041627526

Offset

1,2

Comments

Column 2 of A230250.

Links

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

Formula

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

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

Example

All solutions for n=3:
..0..3....0..1....0..3....0..1....0..1....0..3
..1..2....3..2....1..0....1..2....3..2....1..2
..0..1....0..1....2..3....0..3....2..1....0..3

Crossrefs

Cf. A230250.

Sequence in context: A296217 A050890 A114710 * A358107 A288606 A379163

Adjacent sequences: A230242 A230243 A230244 * A230246 A230247 A230248

Keyword

nonn

Author

R. H. Hardin, Oct 13 2013

Status

approved