A208310 Number of n X 4 0..1 arrays with new values 0..1 introduced in row major order and no element equal to more than one of its immediate leftward or upward neighbors.

8, 54, 336, 2052, 12474, 75744, 459810, 2791152, 16942716, 102844566, 624279960, 3789460422, 23002516080, 139628253924, 847561596858, 5144808733200, 31229655752466, 189568057623696, 1150702676836956, 6984914373637974

Offset

1,1

Comments

Column 4 of A208314.

Links

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

Formula

Empirical: a(n) = 9*a(n-1) - 21*a(n-2) + 21*a(n-3) - 9*a(n-4).

Empirical g.f.: 2*x*(4 - 9*x + 9*x^2 - 3*x^3) / (1 - 9*x + 21*x^2 - 21*x^3 + 9*x^4). - Colin Barker, Jun 30 2018

Example

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

Crossrefs

Cf. A208314.

Sequence in context: A091433 A081899 A057970 * A154235 A289796 A287814

Adjacent sequences: A208307 A208308 A208309 * A208311 A208312 A208313

Keyword

nonn

Author

R. H. Hardin, Feb 25 2012

Status

approved