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

Author

R. H. Hardin, Feb 20 2016

Keywords

• nonn

Examples

			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
		

Links

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

Crossrefs

Row 2 of A269201.

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)