OFFSET
1,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..2800
EXAMPLE
a(20)=34 since 1+phi(34)^2 = 1+16^2 = 257 is prime.
MAPLE
select(t -> isprime(numtheory:-phi(t)^2+1), [$1..1000]); # Robert Israel, Mar 11 2020
MATHEMATICA
Select[Range[200], PrimeQ[1+EulerPhi[#]^2]&] (* Harvey P. Dale, Aug 13 2014 *)
PROG
(PARI) isok(n) = isprime(1 + eulerphi(n)^2) \\ Michel Marcus, Jul 18 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Carmine Suriano, Sep 14 2010
STATUS
approved