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, 15, 196, 2765, 38731, 545328, 7675381, 108065699, 1521488668, 21421955457, 301612441375, 4246586949080, 59790307544569, 841824567122343, 11852566615920436, 166879587240301061, 2349600516714827299

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 * A345445 A152587 A060337

Adjacent sequences: A185896 A185897 A185898 * A185900 A185901 A185902

Keyword

nonn

Author

R. H. Hardin, Feb 06 2011

Status

approved