A073182 Number of divisors of n which are not greater than the cubefree kernel of n.
1, 2, 2, 3, 2, 4, 2, 3, 3, 4, 2, 6, 2, 4, 4, 3, 2, 6, 2, 6, 4, 4, 2, 7, 3, 4, 3, 6, 2, 8, 2, 3, 4, 4, 4, 9, 2, 4, 4, 7, 2, 8, 2, 6, 6, 4, 2, 7, 3, 6, 4, 6, 2, 6, 4, 7, 4, 4, 2, 12, 2, 4, 6, 3, 4, 8, 2, 6, 4, 8, 2, 11, 2, 4, 6, 6, 4, 8, 2, 8, 3, 4, 2, 12, 4, 4, 4, 7, 2, 12, 4, 6, 4, 4, 4, 7, 2, 6, 6, 9, 2, 8
Offset: 1
Keywords
Examples
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) = 7.
Links
- Antti Karttunen, Table of n, a(n) for n = 1..10000
Programs
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Mathematica
Table[Function[k, DivisorSum[n, 1 &, # <= k &]]@ Apply[Times, FactorInteger[n] /. {p_, e_} /; p > 0 :> p^Min[e, 2]], {n, 102}] (* Michael De Vlieger, Jul 18 2017 *) -
PARI
a007948(n) = my(f=factor(n)); for (i=1, #f~, f[i, 2] = min(f[i, 2], 2)); factorback(f); a(n) = my(cfk = a007948(n)); sumdiv(n, d, d<=cfk); \\ Michel Marcus, May 14 2015
Comments