OFFSET
1,2
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
FORMULA
a(n) >= A048250(n).
EXAMPLE
The squarefree kernel of 56 = 7 * 2^3 is 14 = 7*2 and the divisors <= 14 of 56 are {1, 2, 4, 7, 8, 14}, therefore a(56) = 1 + 2 + 4 + 7 + 8 + 14 = 36.
MATHEMATICA
a[n_] := DivisorSum[n, # &, # <= Times @@ FactorInteger[n][[;; , 1]] &]; Array[a, 100] (* Amiram Eldar, Jul 09 2022 *)
PROG
(PARI)
A007947(n) = factorback(factorint(n)[, 1]); \\ This function from Andrew Lelechenko
A073181(n) = sumdiv(n, d, d*(d<=A007947(n))); \\ Antti Karttunen, Sep 10 2017, after Michel Marcus's code for A073183.
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Reinhard Zumkeller, Jul 19 2002
STATUS
approved