A188580 Number of words of length n over an alphabet of size 5 which do not contain a run of 5 identical letters.

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

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