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A183804 1/16 the number of (n+1) X 3 binary arrays with no 2 X 2 subblock being a reflection across the shared element pair of any horizontal or vertical neighbor. 1
3, 13, 55, 237, 1011, 4341, 18567, 79605, 340803, 1460349, 6254199, 26793693, 114763635, 491621157, 2105830791, 9020628261, 38640044547, 165518326125, 709005955383, 3037082133069, 13009525105779, 55727225184213 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 2 of A183811.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n) = 3*a(n-1) + 9*a(n-2) - 15*a(n-3).

Empirical g.f.: x*(3 + 4*x - 11*x^2) / (1 - 3*x - 9*x^2 + 15*x^3). - Colin Barker, Apr 04 2018

EXAMPLE

Some solutions with upper left block zero for 5 X 3:

  0 0 0    0 0 0    0 0 0    0 0 1    0 0 1    0 0 1    0 0 1

  0 0 1    0 0 1    0 0 1    0 0 1    0 0 1    0 0 0    0 0 1

  0 1 1    1 1 1    1 1 1    1 1 0    1 1 0    1 0 0    0 1 0

  0 1 1    1 1 0    1 0 0    1 0 0    1 1 1    0 1 1    1 1 0

  1 1 0    0 1 0    0 0 1    0 0 1    0 0 1    0 1 0    1 1 1

CROSSREFS

Cf. A183811.

Sequence in context: A286191 A033887 A291653 * A117376 A264037 A151318

Adjacent sequences:  A183801 A183802 A183803 * A183805 A183806 A183807

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 07 2011

STATUS

approved

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Last modified August 9 01:35 EDT 2020. Contains 336310 sequences. (Running on oeis4.)