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A221577 Number of 0..n arrays of length 7 with each element differing from at least one neighbor by something other than 1. 1
16, 345, 4240, 26911, 117104, 395641, 1116400, 2754635, 6127696, 12553189, 24049616, 43584535, 75375280, 125247281, 201055024, 313170691, 475045520, 703848925, 1021190416, 1453929359, 2035077616, 2804800105, 3811518320 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 7 of A221573.

LINKS

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

FORMULA

Empirical: a(n) = 1*n^7 + 3*n^6 - 7*n^5 + 29*n^4 - 41*n^3 + 45*n^2 - 33*n + 19 for n>2.

Conjectures from Colin Barker, Aug 08 2018: (Start)

G.f.: x*(16 + 217*x + 1928*x^2 + 1755*x^3 + 2336*x^4 - 1869*x^5 + 1096*x^6 - 579*x^7 + 160*x^8 - 20*x^9) / (1 - x)^8.

a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n>10.

(End)

EXAMPLE

Some solutions for n=6:

..0....4....3....0....4....4....4....3....0....0....3....4....0....0....0....4

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

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

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

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

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

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

CROSSREFS

Cf. A221573.

Sequence in context: A320399 A173906 A227102 * A136269 A010368 A053103

Adjacent sequences: A221574 A221575 A221576 * A221578 A221579 A221580

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 20 2013

STATUS

approved

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Last modified December 2 08:36 EST 2022. Contains 358493 sequences. (Running on oeis4.)