A269215 Number of 2 X n 0..3 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling three exactly once.

0, 96, 768, 6528, 49536, 360960, 2546304, 17563392, 119091072, 796813824, 5274483840, 34608512256, 225420724608, 1459142258688, 9394561013376, 60205610853120, 384263133750144, 2443755614295552, 15491594556534912

Offset: 1

Author

R. H. Hardin, Feb 20 2016

Keywords

• nonn

Comments

Row 2 of A269214.

Examples

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

Links

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

Crossrefs

Cf. A269214.

Formula

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

From Colin Barker, Mar 21 2018: (Start)

G.f.: 96*x^2*(1 - x)^2 / ((1 + x)^2*(1 - 6*x)^2).

a(n) = 8*(175*6^n*n + 1008*n - 55*6^n - 288) / 1029 for n even.

a(n) = 8*(175*6^n*n - 1008*n - 55*6^n + 288) / 1029 for n odd.

(End)