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A377174
Primes p such that 5/2 is a primitive root modulo p.
6
11, 17, 23, 47, 59, 73, 101, 103, 109, 113, 137, 139, 149, 167, 179, 211, 223, 229, 233, 257, 263, 269, 313, 337, 349, 353, 367, 379, 383, 389, 419, 421, 433, 461, 487, 499, 503, 509, 593, 607, 617, 647, 659, 661, 673, 727, 743, 811, 821, 823, 829, 857, 859, 863, 887, 941, 953, 967, 971, 977, 983
OFFSET
1,1
COMMENTS
If p is a term in this sequence, then 5/2 is not a square modulo p (i.e., p is in A038880).
Conjecture: this sequence has relative density equal to Artin's constant (A005596) with respect to the set of primes.
PROG
(PARI) forprime(p=7, 10^3, if(znorder(Mod(5/2, p))==p-1, print1(p, ", ")));
CROSSREFS
Primes p such that +a/2 is a primitive root modulo p: A320384 (a=3), this sequence (a=5), A377176 (a=7), A377178 (a=9).
Primes p such that -a/2 is a primitive root modulo p: A377172 (a=3), A377175 (a=5), A377177 (a=7), A377179 (a=9).
Sequence in context: A031505 A094524 A243817 * A098412 A261918 A136342
KEYWORD
nonn,easy
AUTHOR
Jianing Song, Oct 18 2024
STATUS
approved