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A050982 5-idempotent numbers. +0
10
1, 30, 525, 7000, 78750, 787500, 7218750, 61875000, 502734375, 3910156250, 29326171875, 213281250000, 1510742187500, 10458984375000, 70971679687500, 473144531250000, 3105010986328125, 20091247558593750 (list; graph; listen)
OFFSET

5,2

COMMENT

With a different offset, number of n-permutations of 6 objects:t,u,v,z,x, y with repetition allowed, containing exactly five (5) u's. Example: a(1)=30 because we have uuuuut, uuuutu, uuutuu, uutuuu, utuuuu, tuuuuu, uuuuuv, uuuuvu, uuuvuu, uuvuuu, uvuuuu, vuuuuu, uuuuuz, uuuuzu, uuuzuu, uuzuuu, uzuuuu, zuuuuu, uuuuux, uuuuxu, uuuxuu, uuxuuu, uxuuuu, xuuuuu, uuuuuy, uuuuyu, uuuyuu, uuyuuu, uyuuuu, yuuuuu. - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 16 2008

REFERENCES

L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 91, #43..

LINKS

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

FORMULA

C(n, 5)*5^(n-5).

G.f.:1/(1-5*x)^6. [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 06 2008]

Expansion of 1/(1-5*x)^6. - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 02 2008

MAPLE

seq(binomial(n+5, 5)*5^n, n=0..17); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 16 2008

PROGRAM

(Other) SAGE: [lucas_number2(n, 5, 0)*binomial(n, 5)/5^5 for n in xrange(5, 23)] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 12 2009]

CROSSREFS

Cf. A000027, A001788, A036216, A040075, A050988, A050989.

A000389, A054849, A036219, A045543, A036084, A140404 [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 06 2008]

Cf. A000389, A054849, A036219, A045543, A036084, A140404.

Sequence in context: A118681 A020926 A022754 this_sequence A004327 A139626 A037961

Adjacent sequences: A050979 A050980 A050981 this_sequence A050983 A050984 A050985

KEYWORD

nonn

AUTHOR

Eric Weisstein (eric(AT)weisstein.com)

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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