Primes p for which the polynomial (x^23 - 1)/(x - 1) mod p is irreducible.
5, 7, 11, 17, 19, 23, 37, 43, 53, 61, 67, 79, 83, 89, 97, 103, 107, 109, 113, 149, 157, 181, 191, 199, 227, 241, 251, 263, 281, 283, 293, 313, 337, 359, 373, 379, 383, 389, 401, 419, 421, 431, 433, 457, 467, 479, 503, 521, 523, 557, 563, 569, 571, 613, 617
1
This is the 22nd-degree cyclotomic polynomial. These primes p satisfy the congruence p mod 23 == {0, 5, 7, 10, 11, 14, 15, 17, 19, 20, 21}. The fraction of all primes in this sequence is 5/11. If we plotted n versus primepi(s(n)), then the plotted points would be very close to the line having slope 11/5.
T. D. Noe, Plot of 1000 terms
T. D. Noe, Table of 1000 terms
Wikipedia, Cyclotomic polynomial
(Mma) t = {}; n = 23; p = 1; While[Length[t] < 100, p = NextPrime[p]; If[Length[FactorList[(x^n - 1)/(x - 1), Modulus -> p]] == 2, AppendTo[t, p]]]; t
Cf. A045309, A042993, A045401, S000762-S000782.
nonn
T. D. Noe, Dec 01 2015