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A004154 Omit trailing zeros from factorial numbers. 10
1, 1, 2, 6, 24, 12, 72, 504, 4032, 36288, 36288, 399168, 4790016, 62270208, 871782912, 1307674368, 20922789888, 355687428096, 6402373705728, 121645100408832, 243290200817664, 5109094217170944, 112400072777760768 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..250

Index entries for sequences related to factorial numbers

FORMULA

a(n) = A000142(n) / 10^A027868(n). - Reinhard Zumkeller, Nov 24 2012

a(n+1) = A004151((n+1)*a(n)). - Reinhard Zumkeller, Nov 24 2012, corrected by M. F. Hasler, Oct 16 2014

a(n) = A004151(A000142(n)) = A000142(n)/A011557(A112765(n)), or A122840 instead of A112765. - M. F. Hasler, Oct 16 2014

MATHEMATICA

f[n_] := n!/10^Sum[Floor[n/5^k], {k, 1, Log[10, n] + 1}]; Table[f[n], {n, 0, 22}]

PROG

(Haskell)

a004154 = a004151 . a000142

a004154_list = scanl (\u v -> a004151 $ u * v) 1 [1..]

-- Reinhard Zumkeller, Nov 24 2012

(PARI) a(n)=n!/10^valuation(n!, 5) \\ M. F. Hasler, Oct 16 2014

(MAGMA) [Factorial(n)/10^Valuation(Factorial(n), 5): n in [0..30]]; // Vincenzo Librandi, Oct 16 2014

CROSSREFS

Cf. A000142, A004151.

Sequence in context: A256270 A243657 A321475 * A076126 A263692 A319544

Adjacent sequences:  A004151 A004152 A004153 * A004155 A004156 A004157

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified July 22 07:23 EDT 2019. Contains 325216 sequences. (Running on oeis4.)