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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
OFFSET
1,1
LINKS
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
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jun 29 2015
STATUS
approved