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A186161 1/4 the number of n X 2 0..3 arrays with every element equal to exactly one or two of its horizontal and vertical neighbors. 1
1, 7, 48, 321, 2175, 14748, 99933, 677283, 4590168, 31108893, 210834267, 1428886932, 9683993481, 65631317487, 444803049600, 3014563174089, 20430595384935, 138464249604684, 938413592805957, 6359909317239723 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 2 of A186168.

LINKS

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

FORMULA

Empirical: a(n) = 5*a(n-1) + 11*a(n-2) + 9*a(n-3) - 9*a(n-4) - 27*a(n-5).

Empirical g.f.: x*(1 + 2*x + 2*x^2 - 5*x^3 - 12*x^4) / (1 - 5*x - 11*x^2 - 9*x^3 + 9*x^4 + 27*x^5). - Colin Barker, Apr 17 2018

EXAMPLE

Some solutions for 4 X 2 with a(1,1)=0:

..0..0....0..1....0..0....0..0....0..3....0..2....0..0....0..2....0..2....0..0

..2..2....0..1....2..3....1..1....0..3....0..2....0..2....0..2....0..2....0..0

..0..2....3..3....2..3....3..3....2..0....0..2....3..2....3..3....1..1....2..2

..0..0....0..0....1..1....3..3....2..0....0..2....3..3....3..3....1..1....0..0

CROSSREFS

Cf. A186168.

Sequence in context: A227100 A240334 A171312 * A081106 A289785 A036829

Adjacent sequences:  A186158 A186159 A186160 * A186162 A186163 A186164

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 13 2011

STATUS

approved

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Last modified October 20 14:24 EDT 2021. Contains 348108 sequences. (Running on oeis4.)