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A221517 Number of 0..n arrays of length 6 with each element differing from at least one neighbor by 2 or more, starting with 0. 1
0, 5, 89, 532, 1970, 5513, 12872, 26477, 49598, 86465, 142388, 223877, 338762, 496313, 707360, 984413, 1341782, 1795697, 2364428, 3068405, 3930338, 4975337, 6231032, 7727693, 9498350, 11578913, 14008292, 16828517, 20084858, 23825945 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 6 of A221515.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 1*n^5 - 20*n^3 + 78*n^2 - 146*n + 125 for n>4.

Conjectures from Colin Barker, Aug 06 2018: (Start)

G.f.: x^2*(5 + 59*x + 73*x^2 + 13*x^3 - 32*x^4 + 9*x^5 - 9*x^6 + 3*x^7 - x^8) / (1 - x)^6.

a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>10.

(End)

EXAMPLE

Some solutions for n=6:

..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0

..3....2....6....3....2....5....3....2....5....3....2....4....3....6....5....3

..5....0....5....5....6....2....0....2....1....0....4....0....4....6....6....2

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

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

..0....1....4....6....5....5....5....6....4....3....6....4....4....0....1....5

CROSSREFS

Cf. A221515.

Sequence in context: A176608 A277233 A167735 * A264247 A067257 A134497

Adjacent sequences:  A221514 A221515 A221516 * A221518 A221519 A221520

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 18 2013

STATUS

approved

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Last modified February 17 12:32 EST 2020. Contains 331996 sequences. (Running on oeis4.)