A221466 Number of 0..n arrays of length 7 with each element unequal to at least one neighbor, starting with 0.

8, 240, 1944, 8960, 30000, 81648, 192080, 405504, 787320, 1430000, 2459688, 4043520, 6397664, 9796080, 14580000, 21168128, 30067560, 41885424, 57341240, 77280000, 102685968, 134697200, 174620784, 223948800, 284375000, 357812208

Offset: 1

Author

R. H. Hardin, Jan 17 2013

Keywords

• nonn

Comments

Row 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....4....5....2....5....2....4....4....4....4....1....3....4....6....2....3
..6....4....0....2....4....0....4....3....3....4....2....4....5....4....1....2
..0....5....6....4....0....4....2....6....3....5....2....6....2....6....6....1
..0....3....1....2....1....4....0....4....6....2....0....1....3....5....4....1
..6....6....1....3....0....3....2....4....6....0....2....0....6....4....4....0
..2....2....6....0....6....1....1....3....3....3....5....3....5....6....5....4
		

Links

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

Crossrefs

Cf. A221463.

Formula

Empirical: a(n) = 1*n^6 + 4*n^5 + 3*n^4.

Conjectures from Colin Barker, Aug 05 2018: (Start)

G.f.: 8*x*(1 + 23*x + 54*x^2 + 14*x^3 - 2*x^4) / (1 - x)^7.

a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>7.

(End)