The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A216838 Odd primes for which 2 is not a primitive root. 12
 7, 17, 23, 31, 41, 43, 47, 71, 73, 79, 89, 97, 103, 109, 113, 127, 137, 151, 157, 167, 191, 193, 199, 223, 229, 233, 239, 241, 251, 257, 263, 271, 277, 281, 283, 307, 311, 313, 331, 337, 353, 359, 367, 383, 397, 401, 409, 431, 433, 439, 449, 457, 463, 479 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Alternately, for these primes p, the polynomial (x^p+1)/(x+1) is reducible over GF(2). The prime p belongs to this sequence if and only if A002326((p-1)/2) != (p-1). If A002326((p-1)/2) = (p-1), then the prime p belongs to the sequence A001122. - V. Raman, Dec 01 2012 The only primitive root modulo 2 is 1. See A060749. Hence 2 should be added to this sequence in order to obtain the complement of A001122. - Wolfdieter Lang, May 19 2014 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 MAPLE select(t -> isprime(t) and numtheory[order](2, t) <> t-1, [seq](2*i+1, i=1..1000)); # Robert Israel, May 20 2014 MATHEMATICA Select[Prime[Range[2, 100]], PrimitiveRoot[#] =!= 2 &] (* T. D. Noe, Sep 19 2012 *) PROG (PARI) forprime(p=3, 1000, if(znorder(Mod(2, p))!=p-1, print(p))) (PARI) forprime(p=3, 1000, if(factormod((x^p+1)/(x+1), 2, 1)[1, 1]!=(p-1), print(p))) CROSSREFS Cf. A002326 (multiplicative order of 2 mod 2n+1) Cf. A001122 (Primes for which 2 is a primitive root). Sequence in context: A107643 A289363 A319040 * A198441 A058529 A253408 Adjacent sequences:  A216835 A216836 A216837 * A216839 A216840 A216841 KEYWORD nonn AUTHOR V. Raman, Sep 17 2012 EXTENSIONS Name corrected by Wolfdieter Lang, May 19 2014 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 1 22:01 EDT 2021. Contains 346408 sequences. (Running on oeis4.)