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A185899 1/8 the number of n X 2 0..7 arrays with every element equal to exactly one or two of its horizontal and vertical neighbors. 1
1, 15, 196, 2765, 38731, 545328, 7675381, 108065699, 1521488668, 21421955457, 301612441375, 4246586949080, 59790307544569, 841824567122343, 11852566615920436, 166879587240301061, 2349600516714827299 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 2 of A185903.

LINKS

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

FORMULA

Empirical: a(n) = 13*a(n-1) + 27*a(n-2) - 147*a(n-3) - 245*a(n-4) - 343*a(n-5).

Empirical g.f.: x*(1 + 2*x - 26*x^2 - 41*x^3 - 56*x^4) / (1 - 13*x - 27*x^2 + 147*x^3 + 245*x^4 + 343*x^5). - Colin Barker, Apr 17 2018

EXAMPLE

Some solutions for 3 X 2 with a(1,1)=0:

..0..1....0..0....0..6....0..0....0..0....0..0....0..0....0..0....0..0....0..7

..0..1....7..0....0..6....0..6....4..0....2..2....5..2....1..1....4..4....0..7

..1..1....7..7....5..5....6..6....4..0....3..3....5..2....3..3....1..1....7..7

CROSSREFS

Cf. A185903.

Sequence in context: A015673 A125472 A098300 * A152587 A060337 A180789

Adjacent sequences:  A185896 A185897 A185898 * A185900 A185901 A185902

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 06 2011

STATUS

approved

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Last modified April 17 04:36 EDT 2021. Contains 343059 sequences. (Running on oeis4.)