OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
sopf(sigma(90)) = sopf(234) = 18; sigma(sopf(90)) = sigma(10) = 18, hence 90 is a term of the sequence.
MATHEMATICA
p[n_] := Apply[Plus, Transpose[FactorInteger[n]][[1]]]; Select[Range[2, 10^4], p[DivisorSigma[1, # ]] == DivisorSigma[1, p[ # ]] &]
PROG
(PARI) isok(n) = (n>1) && sigma(sopf(n)) == sopf(sigma(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