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

Author

R. H. Hardin, Aug 17 2015

Keywords

• nonn

Examples

			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
		

Links

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

Crossrefs

Column 2 of A261380.

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