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A206981 Number of n X 2 0..1 arrays avoiding the patterns 0 1 0 or 1 0 1 in any row, column, diagonal or antidiagonal. 32
4, 16, 36, 100, 256, 676, 1764, 4624, 12100, 31684, 82944, 217156, 568516, 1488400, 3896676, 10201636, 26708224, 69923044, 183060900, 479259664, 1254718084, 3284894596, 8599965696, 22515002500, 58945041796, 154320122896, 404015326884 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 2*a(n-1) + 2*a(n-2) - a(n-3). G.f.: -4*x*(-1-2*x+x^2) / ( (1+x)*(x^2-3*x+1) ).
Empirical: a(n) = (A080097(n)+1)*4. - Martin Ettl, Nov 13 2012
EXAMPLE
Some solutions for n=4
..1..1....0..0....0..0....0..0....1..1....0..1....1..1....0..1....1..0....0..0
..0..1....0..1....1..0....1..0....1..1....1..1....1..1....1..0....0..1....1..1
..0..0....1..1....1..1....1..0....1..1....1..0....1..1....1..0....0..1....1..1
..1..0....1..1....0..1....1..0....1..1....1..0....0..0....1..0....1..0....0..0
CROSSREFS
Column 2 of A206987.
Cf. A080097.
Sequence in context: A005722 A372635 A075408 * A318149 A233409 A181795
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 14 2012
STATUS
approved

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Last modified May 26 23:01 EDT 2024. Contains 372847 sequences. (Running on oeis4.)