OFFSET
1,1
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..300
EXAMPLE
sigma(sigma(21) - 21) = sigma(32 - 21) = sigma(11) = 12 = phi(21), so 21 is a term of the sequence.
MATHEMATICA
Select[Range[10^5], DivisorSigma[1, DivisorSigma[1, # ] - # ] == EulerPhi[ # ] &]
CROSSREFS
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Sep 12 2002
EXTENSIONS
a(19)-a(34) from Donovan Johnson, May 13 2010
STATUS
approved