A269291 Number of 3 X n 0..3 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling three no more than once.

64, 2592, 62748, 1363572, 27788292, 544118148, 10363900428, 193439931300, 3554908340004, 64533455294868, 1159917367905324, 20677732339697748, 366084589527655236, 6443257191283855908, 112830460117748363340

Offset: 1

Author

R. H. Hardin, Feb 21 2016

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Row 3 of A269289.

Formula

Empirical: a(n) = 36*a(n-1) - 378*a(n-2) + 972*a(n-3) - 729*a(n-4) for n>7.

Empirical g.f.: 4*x*(16 + 72*x - 1593*x^2 + 5553*x^3 - 13581*x^4 + 17091*x^5 - 6804*x^6) / (1 - 18*x + 27*x^2)^2. - Colin Barker, Jan 21 2019