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
KEYWORD
nonn
AUTHOR
Labos Elemer, Apr 03 2003
STATUS
approved