OFFSET
1,2
COMMENTS
a(n) >= A073185(n).
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
EXAMPLE
The cubefree kernel of 56 = 7 * 2^3 is 28 = 7 * 2^2 and the divisors <= 28 of 56 are {1, 2, 4, 7, 8, 14, 28}, therefore a(56) = 1 + 2 + 4 + 7 + 8 + 14 + 28 = 64.
MATHEMATICA
sdcfk[n_]:=Module[{cf=Times@@Flatten[Table[#[[1]], #[[2]]]&/@({#[[1]], If[ #[[2]]>2, 2, #[[2]]]}&/@FactorInteger[n])]}, Total[Select[Divisors[n], #<= cf&]]]; Array[sdcfk, 80] (* Harvey P. Dale, Jul 14 2018 *)
PROG
(PARI) a007948(n) = my(f=factor(n)); for (i=1, #f~, f[i, 2] = min(f[i, 2], 2)); factorback(f);
a(n) = sumdiv(n, d, d*(d<=a007948(n))); \\ Michel Marcus, Feb 07 2015
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Reinhard Zumkeller, Jul 19 2002
STATUS
approved