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A317649 Numbers whose least primitive root is an odd prime. 2
4, 6, 7, 10, 14, 17, 18, 22, 23, 26, 31, 34, 38, 43, 46, 47, 49, 50, 54, 58, 62, 71, 73, 74, 79, 82, 86, 89, 94, 97, 98, 103, 106, 113, 118, 122, 127, 134, 137, 142, 146, 157, 158, 162, 166, 167, 178, 191, 193, 194, 199, 202, 206, 214, 218, 223, 226, 233, 239, 241, 242, 250, 254, 257, 262, 263 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The first odd number in the sequence whose square is not in the sequence is 40487.

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

a(3)=7 is included because the least primitive root mod 7 is 3, an odd prime.

8 is not included because there is no primitive root mod 8 (the multiplicative group mod 8 is not cyclic).

9 is not included because the least primitive root mod 9 is 2.

MAPLE

filter:= proc(n) local p;

  p:= numtheory:-primroot(n);

  if p = FAIL then return false fi;

  p>2 and isprime(p)

end proc:

select(filter, [$1..1000]);

MATHEMATICA

Select[Range@ 263, If[# == {}, False, And[PrimeQ@ #, # > 2] &@ #[[1]] ] &@ PrimitiveRootList[#] &] (* Michael De Vlieger, Aug 02 2018 *)

PROG

(PARI) isok(n) = my(r=lift(znprimroot(prime(n)))); isprime(r) && (r%2); \\ Michel Marcus, Aug 04 2018

CROSSREFS

Subset of A033948.

Cf. A048976.

Sequence in context: A107622 A049306 A023635 * A265036 A310652 A310653

Adjacent sequences:  A317646 A317647 A317648 * A317650 A317651 A317652

KEYWORD

nonn

AUTHOR

Robert Israel, Aug 02 2018

STATUS

approved

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Last modified March 18 13:47 EDT 2019. Contains 321289 sequences. (Running on oeis4.)