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A221680 Number of 0..5 arrays of length n with each element differing from at least one neighbor by 1 or less, starting with 0. 1
0, 2, 5, 32, 133, 636, 2856, 13169, 60120, 275632, 1261451, 5777107, 26449970, 121113272, 554546205, 2539172736, 11626346343, 53234805475, 243751618738, 1116090939600, 5110360772166, 23399338403512, 107140971422686 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 5 of A221683.

LINKS

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

FORMULA

Empirical: a(n) = 4*a(n-1) +3*a(n-2) -6*a(n-3) +19*a(n-4) +5*a(n-5) +a(n-6).

Empirical g.f.: x^2*(2 - 3*x + 6*x^2 + 2*x^3) / (1 - 4*x - 3*x^2 + 6*x^3 - 19*x^4 - 5*x^5 - x^6). - Colin Barker, Oct 19 2017

EXAMPLE

Some solutions for n=6

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

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

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

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

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

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

CROSSREFS

Sequence in context: A042811 A261045 A145656 * A009274 A019036 A005636

Adjacent sequences: A221677 A221678 A221679 * A221681 A221682 A221683

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 22 2013

STATUS

approved

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Last modified December 4 02:16 EST 2022. Contains 358544 sequences. (Running on oeis4.)