A231773 Numbers k such that there are no numbers with k primitive roots.

3, 5, 7, 9, 11, 13, 14, 15, 17, 19, 21, 23, 25, 26, 27, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 45, 46, 47, 49, 50, 51, 53, 55, 56, 57, 58, 59, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 78, 79, 81, 83, 85, 86, 87, 89, 90, 91, 93, 94, 95

Offset: 1

Author

Arkadiusz Wesolowski, Nov 13 2013

Keywords

• nonn

Comments

Numbers k such that A231772(k) = 0.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A007617, A010554, A046144, A231772.

Programs

PARI

r=95; for(n=2, r, m=0; for(c=2*n+1, n^2+1, if(n%2==1, break); e=eulerphi(c); if(e==lcm(znstar(c)[2])&&eulerphi(e)==n, m=1; break)); if(m==0, print1(n, ", ")));

Formula

a(n) = A007617(n) for n <= 16.