A240478 Number of n X 2 0..1 arrays with no element equal to more than two horizontal or vertical neighbors, with new values 0..1 introduced in row major order.

2, 8, 25, 81, 264, 857, 2785, 9050, 29407, 95557, 310508, 1008981, 3278637, 10653778, 34618955, 112492681, 365539724, 1187804297, 3859714705, 12541963050, 40754524407, 132429927677, 430324878028, 1398320635661, 4543777736197

Offset

1,1

Comments

Column 2 of A240484.

Links

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

Formula

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

Empirical g.f.: x*(2 + 2*x - x^2 - 2*x^3) / (1 - 3*x - x^2 + 2*x^4). - Colin Barker, Feb 24 2018

Example

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

Crossrefs

Cf. A240484.

Sequence in context: A138804 A212323 A301842 * A288539 A281338 A036367

Adjacent sequences: A240475 A240476 A240477 * A240479 A240480 A240481

Keyword

nonn

Author

R. H. Hardin, Apr 06 2014

Status

approved