A259517 Number of (n+1) X (1+1) 0..1 arrays with each 2 X 2 subblock having clockwise pattern 0000 0001 0011 0101 or 1111.

12, 38, 120, 380, 1204, 3816, 12096, 38344, 121552, 385328, 1221520, 3872320, 12275584, 38914656, 123362816, 391070784, 1239728192, 3930045568, 12458584320, 39494789760, 125201899264, 396900848896, 1258210017536, 3988634573824

Offset

1,1

Links

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

Formula

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

Empirical g.f.: 2*x*(2 + x)*(3 - 4*x) / (1 - 4*x + 2*x^2 + 2*x^3). - Colin Barker, Dec 25 2018

Example

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

Crossrefs

Column 1 of A259524.

Sequence in context: A242720 A212510 A213490 * A303619 A167712 A209872

Adjacent sequences: A259514 A259515 A259516 * A259518 A259519 A259520

Keyword

nonn

Author

R. H. Hardin, Jun 29 2015

Status

approved