OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
sopf(phi(203)) = sopf(168) = 12; phi(sopf(203)) = phi(36) = 12 hence 203 is a term of the sequence.
MATHEMATICA
p[n_] := Apply[Plus, Transpose[FactorInteger[n]][[1]]]; Select[Range[3, 10^4], p[EulerPhi[ # ]] == EulerPhi[ p[ # ]] &]
PROG
(PARI) sopf(n) = my(f=factor(n)); sum(j=1, #f~, f[j, 1]); \\ A008472
isok(n) = eulerphi(sopf(n)) == sopf(eulerphi(n)); \\ Michel Marcus, Oct 04 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Oct 18 2002
EXTENSIONS
Edited and extended by Ray Chandler, Feb 13 2005
STATUS
approved