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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. 1
12, 38, 120, 380, 1204, 3816, 12096, 38344, 121552, 385328, 1221520, 3872320, 12275584, 38914656, 123362816, 391070784, 1239728192, 3930045568, 12458584320, 39494789760, 125201899264, 396900848896, 1258210017536, 3988634573824 (list; graph; refs; listen; history; text; internal format)
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

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Last modified September 28 13:24 EDT 2020. Contains 337393 sequences. (Running on oeis4.)