login
A260921
Number of (n+2) X (2+2) 0..1 arrays with each 3 X 3 subblock having clockwise perimeter pattern 00010101 00101011 or 01010101.
1
48, 68, 146, 279, 468, 831, 1528, 2750, 4874, 8781, 15768, 28326, 50656, 91181, 163232, 293511, 525366, 945120, 1691614, 3042584, 5446082, 9796167, 17533998, 31538640, 56451580, 101540858, 181748282, 326914782, 585147672, 1052518323
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = a(n-2) + 6*a(n-4) + 4*a(n-6) - a(n-8) for n>10.
Empirical g.f.: x*(48 + 68*x + 98*x^2 + 211*x^3 + 34*x^4 + 144*x^5 - 8*x^6 - 27*x^7 + 2*x^8 - 3*x^9) / ((1 + x + 2*x^3 - x^4)*(1 - x - 2*x^3 - x^4)). - Colin Barker, Dec 29 2018
EXAMPLE
Some solutions for n=4:
..0..1..0..1....0..0..1..0....1..0..1..0....0..1..0..0....1..0..0..1
..0..0..1..0....1..0..0..1....0..1..0..0....1..0..1..0....1..0..1..0
..0..1..0..0....1..0..1..0....1..0..1..0....0..1..0..1....0..1..0..1
..1..0..1..0....0..1..0..1....0..1..0..1....1..0..0..0....0..0..1..0
..0..1..0..1....0..0..1..0....1..0..0..0....0..1..0..1....0..1..0..0
..1..0..0..1....1..1..0..0....0..1..0..0....1..0..1..0....1..0..1..0
CROSSREFS
Column 2 of A260927.
Sequence in context: A217139 A241481 A100409 * A043157 A039334 A043937
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 04 2015
STATUS
approved