A221462 Number of 0..7 arrays of length n with each element unequal to at least one neighbor, starting with 0.

0, 7, 49, 392, 3087, 24353, 192080, 1515031, 11949777, 94253656, 743424031, 5863743809, 46250174880, 364797430823, 2877333239921, 22694914695208, 179005735545903, 1411904551687777, 11136372010635760, 87837935936264759

Offset: 1

Author

R. H. Hardin Jan 17 2013

Keywords

• nonn

Comments

Column 7 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....5....5....7....7....1....7....4....1....3....1....4....2....5....6....1
..1....4....5....3....2....2....4....7....1....5....2....3....5....2....7....2
..1....1....0....4....0....3....6....5....2....1....4....3....1....7....3....5
..4....6....4....4....3....7....1....2....1....1....2....0....0....4....5....1
..2....2....6....7....0....1....2....0....5....2....1....4....6....0....0....0
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..134

Formula

Empirical: a(n) = 7*a(n-1) +7*a(n-2)