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A221525 Number of 0..n arrays of length 5 with each element differing from at least one neighbor by 2 or more. 1
0, 6, 94, 536, 1940, 5368, 12458, 25544, 47776, 83240, 137078, 215608, 326444, 478616, 682690, 950888, 1297208, 1737544, 2289806, 2974040, 3812548, 4830008, 6053594, 7513096, 9241040, 11272808, 13646758, 16404344, 19590236, 23252440 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 5 of A221524.

LINKS

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

FORMULA

Empirical: a(n) = 1*n^5 - 1*n^4 - 10*n^3 + 38*n^2 - 60*n + 40 for n>2.

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

G.f.: 2*x^2*(3 + 29*x + 31*x^2 + 7*x^3 - 11*x^4 + 2*x^5 - x^6) / (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>8.

(End)

EXAMPLE

Some solutions for n=6:

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

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

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

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

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

CROSSREFS

Cf. A221524.

Sequence in context: A033935 A218682 A078103 * A321073 A198257 A296820

Adjacent sequences:  A221522 A221523 A221524 * A221526 A221527 A221528

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 19 2013

STATUS

approved

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Last modified March 4 02:39 EST 2021. Contains 341774 sequences. (Running on oeis4.)