OFFSET
1,2
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
sopf(sigma(14)) = 5; sopf(phi(14)) = 5; hence 14 is a term of the sequence.
MATHEMATICA
p[n_] := Apply[Plus, Transpose[FactorInteger[n]][[1]]]; Select[Range[3, 10^4], p[DivisorSigma[1, # ]] == p[EulerPhi[ # ]] &]
Select[Range[3000], Total[FactorInteger[DivisorSigma[1, #]][[All, 1]]] == Total[ FactorInteger[EulerPhi[#]][[All, 1]]]&] (* Harvey P. Dale, Sep 20 2016 *)
PROG
(PARI) sopf(n)=my(f=factor(n)[, 1]); sum(i=1, #f, f[i])
is(n)=sopf(sigma(n))==sopf(eulerphi(n)) \\ Charles R Greathouse IV, Mar 09 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Oct 18 2002
EXTENSIONS
Edited by Ray Chandler, Feb 13 2005
a(1) inserted by Charles R Greathouse IV, Mar 09 2014
STATUS
approved