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A025281
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a(n) = sopfr(n!), where sopfr = A001414 is the integer log.
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8
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0, 0, 2, 5, 9, 14, 19, 26, 32, 38, 45, 56, 63, 76, 85, 93, 101, 118, 126, 145, 154, 164, 177, 200, 209, 219, 234, 243, 254, 283, 293, 324, 334, 348, 367, 379, 389, 426, 447, 463, 474, 515, 527, 570, 585, 596, 621, 668, 679, 693, 705, 725, 742, 795, 806, 822, 835, 857, 888
(list;
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OFFSET
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0,3
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REFERENCES
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József Sándor, Dragoslav S. Mitrinovic and Borislav Crstici, Handbook of Number Theory I, Springer Science & Business Media, 2005, Chapter IV, p. 144.
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LINKS
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FORMULA
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a(0)=0; for n>0, a(n) = Sum_{k=1..n} A001414(k).
Asymptotic formula: a(n) ~ (Pi^2/12)*n^2/log(n). [Proven by Alladi and Erdős (1977). - Amiram Eldar, Mar 04 2021]
(End)
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MAPLE
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a:= proc(n) option remember; `if`(n<2, 0,
a(n-1)+add(i[1]*i[2], i=ifactors(n)[2]))
end:
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MATHEMATICA
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sopfr[n_] := Plus @@ Times @@@ FactorInteger@ n; a[n_] := a[n] = a[n - 1] + sopfr[n]; a[0] = a[1] = 0; Array[a, 59, 0] (* Robert G. Wilson v, May 18 2015 *)
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PROG
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(PARI) for(n=1, 100, print1(sum(k=1, n, sum(i=1, omega(k), component(component(factor(k), 1), i)*component(component(factor(k), 2), i))), ", "))
(Python)
from sympy import factorial, factorint
def A025281(n): return sum(p*e for p, e in factorint(factorial(n)).items()) # Chai Wah Wu, Apr 09 2021
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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