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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 (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>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

Adjacent sequences:  A260918 A260919 A260920 * A260922 A260923 A260924

KEYWORD

nonn

AUTHOR

R. H. Hardin, Aug 04 2015

STATUS

approved

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Last modified January 24 13:24 EST 2020. Contains 331193 sequences. (Running on oeis4.)