OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
14 is in the sequence because (phi(14))^2+phi(14)+1 = 6^2+6+1 = 43, which is a prime number.
MATHEMATICA
f[x_] := x^2 + x + 1; Select[Range[250], PrimeQ[f[EulerPhi[#]]] &] (* Amiram Eldar, Feb 08 2021 *)
PROG
(PARI) lista(nn) = {for (n = 1, nn, if (isprime((eulerphi(n))^2 + eulerphi(n) + 1), print1(n, ", ")); ); } \\ Michel Marcus, Jun 01 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), Apr 24 2006
EXTENSIONS
Corrected by Michel Marcus, Jun 01 2013
STATUS
approved