A221461 Number of 0..6 arrays of length n with each element unequal to at least one neighbor, starting with 0.

0, 6, 36, 252, 1728, 11880, 81648, 561168, 3856896, 26508384, 182191680, 1252200384, 8606352384, 59151316608, 406546013952, 2794183983360, 19204379983872, 131991383803392, 907174582723584, 6234995799161856

Offset: 1

Author

R. H. Hardin Jan 17 2013

Keywords

• nonn

Comments

Column 6 of A221463

Examples

			Some solutions for n=6
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..6....4....2....3....2....4....2....6....3....3....1....2....1....5....5....3
..3....2....5....0....2....5....1....6....2....1....2....4....4....5....0....3
..4....4....4....3....6....3....2....2....0....4....2....0....0....4....0....0
..4....3....6....6....1....5....2....2....5....6....3....4....3....0....5....3
..6....4....4....2....6....0....3....4....3....2....6....2....6....4....1....4
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..135

Formula

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