OFFSET
1,2
COMMENTS
a(15) > 10^13.
MATHEMATICA
ad[1]=0; ad[n_]:=n*Total[(#1[[2]] / #1[[1]]&) /@ FactorInteger[n]]; Select[Range[500000], ad[#] == DivisorSigma[1, #] - EulerPhi[#] &]
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Resta, Mar 13 2014
STATUS
approved