A269277 Number of 2 X n 0..3 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling three exactly once.

0, 108, 1368, 13896, 127512, 1104264, 9211608, 74853576, 596581272, 4684312584, 36347893848, 279339197256, 2129701963032, 16128206816904, 121439499248088, 909870855444936, 6787656513072792, 50443519266217224, 373614100586474328

Offset

1,2

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 14*a(n-1) - 49*a(n-2) for n>4.

Conjectures from Colin Barker, Jan 21 2019: (Start)

G.f.: 36*x^2*(3 - x)*(1 - x) / (1 - 7*x)^2.

a(n) = 72 * 7^(n-4) * (60*n-47) for n>2.

(End)

Example

Some solutions for n=4:
..0..0..2..2. .3..3..1..0. .1..2..2..0. .2..0..2..2. .2..2..2..3
..0..3..2..3. .1..1..3..2. .2..0..2..2. .1..2..0..0. .1..0..1..1

Crossrefs

Row 2 of A269276.

Sequence in context: A202484 A096953 A187302 * A115135 A202309 A279981

Adjacent sequences: A269274 A269275 A269276 * A269278 A269279 A269280

Keyword

nonn

Author

R. H. Hardin, Feb 21 2016

Status

approved