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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
OFFSET
1,1
COMMENTS
Column 2 of A183811.
LINKS
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
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 07 2011
STATUS
approved