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A259217
Number of (n+1) X (3+1) 0..1 arrays with each 2 X 2 subblock having clockwise pattern 0000 0011 or 0101.
2
24, 40, 66, 112, 192, 334, 588, 1048, 1890, 3448, 6360, 11854, 22308, 42352, 81042, 156160, 302736, 589966, 1154844, 2269096, 4472514, 8838760, 17505576, 34732942, 69015732, 137303104, 273427698, 544948528, 1086811680, 2168631118, 4329184620
OFFSET
1,1
FORMULA
a(n) = 4*a(n-1) - 4*a(n-2) - a(n-3) + 2*a(n-4).
G.f.: 2*x*(12 - 28*x + x^2 + 16*x^3) / ((1 - x)*(1 - 2*x)*(1 - x - x^2)). - Colin Barker, Dec 24 2018
a(n) = 2^(n+1)+2+6*A000045(n+3). - R. J. Mathar, Oct 09 2020
EXAMPLE
Some solutions for n=4:
..1..0..1..0....1..0..1..0....1..0..0..1....0..1..0..1....0..0..0..0
..0..1..0..1....0..1..0..1....0..1..1..0....1..0..1..0....1..1..1..1
..0..1..0..1....1..0..1..0....1..0..0..1....1..0..1..0....0..0..0..0
..0..1..0..1....0..1..0..1....0..1..1..0....1..0..1..0....0..0..0..0
..1..0..1..0....0..1..0..1....1..0..0..1....1..0..1..0....1..1..1..1
CROSSREFS
Column 3 of A259222.
Sequence in context: A366675 A195562 A026040 * A211567 A316271 A357699
KEYWORD
nonn,easy
AUTHOR
R. H. Hardin, Jun 21 2015
STATUS
approved