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 A242752 Primes p such that pi(p) is a primitive root modulo p, where pi(p) is the number of primes not exceeding p. 6
 2, 3, 5, 13, 17, 29, 31, 41, 47, 61, 89, 101, 107, 137, 167, 179, 193, 197, 223, 229, 251, 257, 263, 271, 293, 313, 337, 347, 353, 379, 401, 431, 439, 487, 499, 587, 593, 599, 601, 643, 647, 653, 659, 677, 701, 727, 733, 739, 751, 797, 821, 823, 829, 857, 919, 929, 941, 967, 971, 983 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS According to the conjecture in A232748, this sequence should contain infinitely many primes. LINKS Zhi-Wei Sun, Table of n, a(n) for n = 1..10000 EXAMPLE a(3) = 5 since 5 is prime with pi(5) = 3 a primitive root modulo 5. 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, " ", Prime[k]]; Label[aa]; Continue, {k, 1, 166}] CROSSREFS Cf. A000040, A000720, A242748, A242750. Sequence in context: A186945 A193761 A215355 * A215813 A235638 A227829 Adjacent sequences:  A242749 A242750 A242751 * A242753 A242754 A242755 KEYWORD nonn AUTHOR Zhi-Wei Sun, May 21 2014 STATUS approved

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Last modified October 23 23:05 EDT 2019. Contains 328379 sequences. (Running on oeis4.)