OFFSET
1,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
205 + phi(205) + sigma(205) = 617 (prime).
MATHEMATICA
Select[Range[500], PrimeQ[#+EulerPhi[#]+DivisorSigma[1, #]]&] (* Harvey P. Dale, Nov 09 2014 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Resta, Feb 13 2006
STATUS
approved