A269202 Number of 2 X n 0..3 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling three no more than once.

16, 180, 1284, 9612, 68052, 472044, 3212820, 21562476, 143085588, 940780908, 6138286356, 39791327340, 256517615124, 1645723601772, 10514049071892, 66922539204204, 424564703856660, 2685565034934636, 16942451080369428

Offset

1,1

Links

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

Formula

Empirical: a(n) = 10*a(n-1) - 13*a(n-2) - 60*a(n-3) - 36*a(n-4).

Conjectures from Colin Barker, Jan 20 2019: (Start)

G.f.: 4*x*(4 + 5*x - 77*x^2 + 18*x^3) / ((1 + x)^2*(1 - 6*x)^2).

a(n) = (6*(-678*(-1)^n+335*6^n) + 56*(144*(-1)^n+25*6^n)*n) / 1029.

(End)

Example

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

Crossrefs

Row 2 of A269201.

Sequence in context: A181239 A021084 A227557 * A269103 A016305 A218895

Adjacent sequences: A269199 A269200 A269201 * A269203 A269204 A269205

Keyword

nonn

Author

R. H. Hardin, Feb 20 2016

Status

approved