OFFSET
1,1
COMMENTS
The sequence appears to be infinite, but I have no proof.
EXAMPLE
a(5) = 21 since 5 + phi(21)^3 = 5 + 12^3 = 1733 is prime.
MATHEMATICA
Select[Range[300], PrimeQ[5+EulerPhi[#]^3]&] (* Harvey P. Dale, Oct 13 2024 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Carmine Suriano, Sep 14 2010
STATUS
approved