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A377175
Primes p such that -5/2 is a primitive root modulo p.
6
3, 17, 31, 43, 67, 71, 73, 79, 83, 101, 107, 109, 113, 137, 149, 163, 191, 199, 227, 229, 233, 239, 257, 269, 271, 283, 307, 311, 313, 337, 347, 349, 353, 359, 389, 421, 431, 433, 439, 443, 461, 467, 479, 509, 547, 563, 587, 593, 599, 617, 631, 661, 673, 683, 719, 821, 827, 829, 839, 857, 907, 911, 919, 941, 947, 953, 977
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 A296925).
Conjecture: this sequence has relative density equal to Artin's constant (A005596) with respect to the set of primes.
PROG
(PARI) print1(3, ", "); 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), A377174 (a=5), A377176 (a=7), A377178 (a=9).
Primes p such that -a/2 is a primitive root modulo p: A377172 (a=3), this sequence (a=5), A377177 (a=7), A377179 (a=9).
Sequence in context: A090648 A031024 A365234 * A045437 A343413 A321796
KEYWORD
nonn,easy
AUTHOR
Jianing Song, Oct 18 2024
STATUS
approved