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A246839
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Number of trailing zeros in A002109(n).
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3
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0, 0, 0, 0, 0, 5, 5, 5, 5, 5, 15, 15, 15, 15, 15, 30, 30, 30, 30, 30, 50, 50, 50, 50, 50, 100, 100, 100, 100, 100, 130, 130, 130, 130, 130, 165, 165, 165, 165, 165, 205, 205, 205, 205, 205, 250, 250, 250, 250, 250, 350, 350, 350, 350, 350, 405, 405, 405, 405
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listen;
history;
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OFFSET
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0,6
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LINKS
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FORMULA
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a(n) = Sum_{i=1..n} i*v_5(i), where v_5(i) = A112765(i) is the exponent of the highest power of 5 dividing i. After a similar formula in A249152. (End)
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MATHEMATICA
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(n=#; k=0; While[Mod[n, 10]==0, n=n/10; k++]; k)&/@Hyperfactorial@Range[0, 60] (* Giorgos Kalogeropoulos, Sep 14 2021 *)
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PROG
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(Python)
def a(n):
..s = 1
..for k in range(n+1):
....s *= k**k
..i = 1
..while not s % 10**i:
....i += 1
..return i-1
n = 1
while n < 100:
..print(a(n), end=', ')
(Python)
from sympy import multiplicity
for n in range(5, 10**3, 5):
....p5 += multiplicity(5, n)*n
(PARI) a(n) = sum(i=1, n, i*valuation(i, 5)); \\ Michel Marcus, Sep 14 2021
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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