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A221466 Number of 0..n arrays of length 7 with each element unequal to at least one neighbor, starting with 0. 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 7 of A221463.

LINKS

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

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)

EXAMPLE

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

CROSSREFS

Cf. A221463.

Sequence in context: A240431 A222688 A254927 * A067360 A221770 A007060

Adjacent sequences:  A221463 A221464 A221465 * A221467 A221468 A221469

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 17 2013

STATUS

approved

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Last modified May 27 06:24 EDT 2019. Contains 323599 sequences. (Running on oeis4.)