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A221686 Number of 0..n arrays of length 7 with each element differing from at least one neighbor by 1 or less, starting with 0. 1
64, 320, 844, 1692, 2856, 4326, 6102, 8184, 10572, 13266, 16266, 19572, 23184, 27102, 31326, 35856, 40692, 45834, 51282, 57036, 63096, 69462, 76134, 83112, 90396, 97986, 105882, 114084, 122592, 131406, 140526, 149952, 159684, 169722, 180066, 190716 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 7 of A221683.

LINKS

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

FORMULA

Empirical: a(n) = 153*n^2 - 213*n + 96 for n>3.

Conjectures from Colin Barker, Aug 10 2018: (Start)

G.f.: 2*x*(32 + 64*x + 38*x^2 + 28*x^3 - 4*x^4 - 5*x^5) / (1 - x)^3.

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>6.

(End)

EXAMPLE

Some solutions for n=6:

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

..1....0....1....0....0....1....0....1....0....0....0....0....0....0....1....1

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

..3....1....0....1....1....5....0....3....2....1....3....3....3....1....2....2

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

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

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

CROSSREFS

Cf. A221683.

Sequence in context: A251196 A221486 A231942 * A211258 A252080 A017366

Adjacent sequences:  A221683 A221684 A221685 * A221687 A221688 A221689

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 22 2013

STATUS

approved

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Last modified October 22 19:03 EDT 2020. Contains 337953 sequences. (Running on oeis4.)