A202796 Number of n X 2 binary arrays with every one adjacent to another one horizontally or vertically.

2, 10, 36, 126, 454, 1632, 5854, 21010, 75412, 270662, 971438, 3486624, 12513958, 44914250, 161203204, 578579694, 2076599286, 7453190368, 26750489166, 96011055010, 344596415668, 1236802258678, 4439047411742, 15932330156576

Offset

1,1

Comments

Column 2 of A202802.

Links

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

Formula

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

Empirical g.f.: 2*x*(1 + 2*x + 2*x^2) / (1 - 3*x - x^2 - 4*x^3). - Colin Barker, Feb 20 2018

Example

Some solutions for n=5:
..0..1....0..0....0..1....1..0....0..0....1..0....1..1....0..1....0..1....1..0
..0..1....1..0....1..1....1..0....0..0....1..0....1..1....1..1....1..1....1..1
..1..1....1..1....1..1....1..1....0..1....0..0....1..0....0..0....1..0....0..1
..1..1....0..1....1..0....1..0....0..1....0..1....0..1....1..0....0..0....1..0
..1..0....1..1....1..0....1..0....0..0....0..1....1..1....1..1....0..0....1..0

Crossrefs

Cf. A202802.

Sequence in context: A266942 A265844 A192858 * A335559 A001582 A357035

Adjacent sequences: A202793 A202794 A202795 * A202797 A202798 A202799

Keyword

nonn

Author

R. H. Hardin, Dec 24 2011

Status

approved