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A082054
Sum of common prime divisors (without multiplicity) of sigma(n) and phi(n).
4
0, 0, 2, 0, 2, 2, 2, 0, 0, 2, 2, 2, 2, 5, 2, 0, 2, 3, 2, 2, 2, 2, 2, 2, 0, 5, 2, 2, 2, 2, 2, 0, 2, 2, 5, 0, 2, 5, 2, 2, 2, 5, 2, 2, 5, 2, 2, 2, 3, 0, 2, 2, 2, 5, 2, 5, 2, 2, 2, 2, 2, 5, 2, 0, 5, 2, 2, 2, 2, 5, 2, 3, 2, 5, 2, 2, 5, 5, 2, 2, 0, 2, 2, 2, 2, 5, 2, 7, 2, 5, 2, 2, 2, 2, 5, 2, 2, 3, 5, 0, 2, 2, 2, 5, 5
OFFSET
1,3
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
MATHEMATICA
ffi[x_] := Flatten[FactorInteger[x]] lf[x_] := Length[FactorInteger[x]] ba[x_] := Table[Part[ffi[x], 2*w-1], {w, 1, lf[x]}] Table[Apply[Plus, Intersection[ba[EulerPhi[w]], ba[DivisorSigma[1, w]]]], {w, 1, 256}]
PROG
(PARI) a(n)=my(f=factor(gcd(sigma(n=factor(n)), eulerphi(n)))[, 1]); sum(i=1, #f, f[i]) \\ Charles R Greathouse IV, Dec 09 2013
CROSSREFS
Sequence in context: A350151 A341846 A262670 * A327276 A044943 A292118
KEYWORD
nonn
AUTHOR
Labos Elemer, Apr 03 2003
STATUS
approved