OFFSET
1,1
EXAMPLE
3 = phi(1)+phi(2)+phi(3)-1 ==> 3, a prime, so 3 is a term.
5 = phi(1)+phi(2)+phi(3)+phi(4)-1 ==> 4, not a prime, so 5 is not a term.
MAPLE
with(numtheory): select(n-> isprime(add(phi(x), x=1..n)-1), [$1..300])[]; # Emeric Deutsch, Jul 20 2005
PROG
(PARI) isok(n) = isprime(sum(k=1, n, eulerphi(k))-1); \\ Michel Marcus, Aug 21 2019
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jorge Coveiro, Dec 22 2004
EXTENSIONS
More terms from Emeric Deutsch, Jul 20 2005
Name edited by Michel Marcus, Aug 21 2019
STATUS
approved