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.

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

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