OFFSET
1,2
COMMENTS
According to the conjecture in A242748, this sequence should have infinitely many terms.
LINKS
Zhi-Wei Sun, Table of n, a(n) for n = 1..10000
EXAMPLE
6 is a member since 6 is a primitive root modulo prime(6) = 13, but 4 and 5 are not since 4 is not a primitive root modulo prime(4) = 7 and 5 is not a primitive root modulo prime(5) = 11.
MATHEMATICA
dv[n_]:=Divisors[n]
n=0; Do[Do[If[Mod[k^(Part[dv[Prime[k]-1], j]), Prime[k]]==1, Goto[aa]], {j, 1, Length[dv[Prime[k]-1]]-1}]; n=n+1; Print[n, " ", k]; Label[aa]; Continue, {k, 1, 195}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Zhi-Wei Sun, May 21 2014
STATUS
approved