Voozh

A221397

Number of n X 3 arrays of occupancy after each element moves to some horizontal, diagonal or antidiagonal neighbor, with no 2-loops and with no occupancy greater than 2.

0, 6, 30, 144, 672, 3108, 14328, 65976, 303672, 1397520, 6431136, 29594352, 136184256, 626677152, 2883768672, 13270180608, 61065117312, 281002082880, 1293081432192, 5950345861248, 27381582408576, 126001256419584

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

Column 3 of A221400.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..41

FORMULA

Empirical: a(n) = 6*a(n-1) - 6*a(n-2) -2*a(n-3).

Empirical g.f.: 6*x^2*(1 - x) / (1 - 6*x + 6*x^2 + 2*x^3). - Colin Barker, Aug 05 2018

EXAMPLE

Some solutions for n=3: