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A296682
Number of n X 2 0..1 arrays with each 1 adjacent to 1, 2 or 3 king-move neighboring 1s.
1
2, 12, 43, 145, 524, 1888, 6737, 24093, 86250, 308600, 1104107, 3950629, 14135676, 50578004, 180970841, 647524153, 2316876914, 8289912724, 29661766587, 106131439497, 379744147900, 1358745529912, 4861666537265, 17395311311589
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 3*a(n-1) - a(n-2) + 11*a(n-3) - 2*a(n-4) + 8*a(n-5) - 4*a(n-6).
Empirical g.f.: x*(2 + 6*x + 9*x^2 + 6*x^3 + 4*x^4 - 4*x^5) / (1 - 3*x + x^2 - 11*x^3 + 2*x^4 - 8*x^5 + 4*x^6). - Colin Barker, Feb 24 2019
EXAMPLE
Some solutions for n=7:
..1..1. .1..0. .0..1. .1..0. .0..1. .1..0. .0..1. .1..0. .0..1. .1..0
..0..1. .1..1. .0..1. .1..1. .1..0. .1..1. .0..1. .1..0. .1..0. .1..1
..0..1. .0..1. .0..1. .0..1. .0..0. .0..0. .0..1. .1..0. .1..0. .0..1
..0..0. .0..0. .0..0. .1..0. .1..1. .0..0. .0..0. .1..1. .0..1. .0..1
..1..1. .1..1. .0..1. .1..0. .0..1. .1..0. .1..1. .0..0. .1..0. .0..1
..0..1. .1..0. .1..1. .1..1. .1..0. .1..0. .1..0. .1..1. .1..0. .1..0
..1..0. .0..0. .1..0. .0..0. .1..0. .1..0. .0..1. .0..1. .0..1. .1..0
CROSSREFS
Column 2 of A296688.
Sequence in context: A189491 A301556 A055681 * A351616 A111389 A203278
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 18 2017
STATUS
approved