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A004154 a(n) = n! with trailing zeros omitted. 13
1, 1, 2, 6, 24, 12, 72, 504, 4032, 36288, 36288, 399168, 4790016, 62270208, 871782912, 1307674368, 20922789888, 355687428096, 6402373705728, 121645100408832, 243290200817664, 5109094217170944, 112400072777760768, 2585201673888497664, 62044840173323943936 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
LINKS
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
MAPLE
a:= n-> (f-> f/10^padic[ordp](f, 10))(n!):
seq(a(n), n=0..29); # Alois P. Heinz, Dec 29 2021
MATHEMATICA
Array[#!//.x_/; x~Mod~5==0:>x/10&, 22] (* Giorgos Kalogeropoulos, Aug 17 2020 *)
Join[{1, 1, 2, 6, 24}, Table[FromDigits[Flatten[Most[Split[IntegerDigits[n!]]]]], {n, 5, 30}]] (* or *) Table[n!/10^IntegerExponent[n!, 10], {n, 0, 30}] (* Harvey P. Dale, Feb 13 2024 *)
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, A008904 (mod 10).
Sequence in context: A243657 A321475 A356757 * A076126 A263692 A363962
KEYWORD
nonn,base
AUTHOR
STATUS
approved

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Last modified March 28 18:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)