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A261106 Number of (n+2) X (1+2) 0..1 arrays with each 3 X 3 subblock having clockwise perimeter pattern 00010001 00010101 or 01010101. 1
28, 33, 63, 97, 183, 289, 547, 865, 1639, 2593, 4915, 7777, 14743, 23329, 44227, 69985, 132679, 209953, 398035, 629857, 1194103, 1889569, 3582307, 5668705, 10746919, 17006113, 32240755, 51018337, 96722263, 153055009, 290166787, 459165025 (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-1) + 3*a(n-2) - 3*a(n-3) for n>6.

Empirical g.f.: x*(28 + 5*x - 54*x^2 + 19*x^3 - 4*x^4 + 4*x^5) / ((1 - x)*(1 - 3*x^2)). - Colin Barker, Dec 30 2018

EXAMPLE

Some solutions for n=4:

..0..1..0....1..0..0....1..0..0....0..0..0....0..1..0....1..0..0....0..1..0

..0..0..1....0..0..0....0..1..0....1..0..1....0..1..0....0..1..0....1..0..1

..0..1..0....1..0..1....1..0..1....0..1..0....0..1..0....0..0..1....0..1..0

..1..0..1....0..0..0....0..0..0....1..0..1....0..1..0....0..1..0....1..0..0

..0..0..0....1..0..1....1..0..1....0..1..0....0..1..0....1..0..1....0..1..0

..1..0..0....0..1..0....0..0..0....0..0..1....0..1..0....0..1..0....0..0..1

CROSSREFS

Column 1 of A261113.

Sequence in context: A261113 A280649 A134657 * A138687 A214470 A055576

Adjacent sequences:  A261103 A261104 A261105 * A261107 A261108 A261109

KEYWORD

nonn

AUTHOR

R. H. Hardin, Aug 08 2015

STATUS

approved

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Last modified May 19 05:05 EDT 2019. Contains 323377 sequences. (Running on oeis4.)