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A261374 Number of (n+2) X (2+2) 0..1 arrays with each 3 X 3 subblock having clockwise perimeter pattern 00001011 00010101 or 01010101. 1
39, 41, 82, 157, 266, 470, 864, 1553, 2758, 4960, 8924, 16001, 28662, 51503, 92374, 165796, 297284, 533858, 957252, 1718645, 3081790, 5533474, 9922064, 17814980, 31944528, 57356546, 102846820, 184661677, 331120454, 594527399, 1066057422 (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) = a(n-2) + 6*a(n-4) + 4*a(n-6) - a(n-8) for n > 9.

Empirical g.f.: x*(39 + 41*x + 43*x^2 + 116*x^3 - 50*x^4 + 67*x^5 - 50*x^6 - 23*x^7 + 9*x^8) / ((1 + x + 2*x^3 - x^4)*(1 - x - 2*x^3 - x^4)). - Colin Barker, Dec 30 2018

EXAMPLE

Some solutions for n=4:

  0 1 0 1     0 0 1 0     1 0 0 1     0 1 0 0     1 0 0 0

  1 0 1 0     0 0 0 1     1 0 0 0     1 0 0 0     0 1 0 1

  0 1 0 1     1 0 1 0     0 1 0 1     0 1 0 1     1 0 1 0

  1 0 1 0     0 1 0 1     1 0 1 0     1 0 1 0     0 0 0 1

  0 1 0 1     0 0 1 0     0 1 0 1     0 1 0 0     0 0 1 0

  1 0 1 0     0 1 0 1     1 0 0 0     0 0 1 0     1 1 0 1

CROSSREFS

Column 2 of A261380.

Sequence in context: A050774 A041759 A257442 * A309696 A061756 A236673

Adjacent sequences:  A261371 A261372 A261373 * A261375 A261376 A261377

KEYWORD

nonn

AUTHOR

R. H. Hardin, Aug 17 2015

STATUS

approved

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Last modified May 17 17:25 EDT 2021. Contains 343983 sequences. (Running on oeis4.)