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A206981 Number of nX2 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

COMMENTS

Column 2 of A206987

LINKS

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

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

Sequence in context: A189145 A005722 A075408 * A318149 A233409 A181795

Adjacent sequences:  A206978 A206979 A206980 * A206982 A206983 A206984

KEYWORD

nonn

AUTHOR

R. H. Hardin Feb 14 2012

STATUS

approved

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Last modified January 24 07:13 EST 2021. Contains 340398 sequences. (Running on oeis4.)