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A188580 Number of words of length n over an alphabet of size 5 which do not contain a run of 5 identical letters. 1
1, 5, 25, 125, 625, 3120, 15580, 77800, 388500, 1940000, 9687520, 48375280, 241565200, 1206272000, 6023600000, 30079249920, 150202748480, 750047481600, 3745412320000, 18702967200000, 93394519000320, 466371784007680, 2328858730112000, 11629312001280000, 58071748137600000, 289985162611998720, 1448060325923962880, 7230986194699366400 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

This is the case M=5 of the general problem mentioned in A188714.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

FORMULA

G.f.: (1+x+x^2+x^3+x^4)/(1-4*x-4*x^2-4*x^3-4*x^4).

MAPLE

See A188714.

MATHEMATICA

CoefficientList[Series[(1 + x + x^2 + x^3 + x^4)/(1 - 4*x - 4*x^2 - 4*x^3 - 4*x^4), {x, 0, 40}], x] (* Vincenzo Librandi, Dec 09 2012 *)

CROSSREFS

Cf. A040000, A121907, A188714.

Sequence in context: A216125 A057831 A014946 * A132839 A206451 A291164

Adjacent sequences:  A188577 A188578 A188579 * A188581 A188582 A188583

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Apr 09 2011

STATUS

approved

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Last modified October 20 22:22 EDT 2021. Contains 348119 sequences. (Running on oeis4.)