

A268629


Primes p that have no squareful primitive roots less than p.


0



3, 5, 7, 13, 17, 19, 23, 31, 41, 43, 47, 61, 71, 73, 79, 97, 103, 127, 191, 193, 223, 239, 241, 311, 313, 337, 409, 433, 439, 457, 479, 601, 719, 769, 839, 911, 1009, 1031, 1033, 1129, 1151, 1201, 1249, 1319, 1321, 1559, 1801, 2089, 2281, 2521, 2689, 2999, 3049, 3361, 3529, 3889
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OFFSET

1,1


LINKS

Table of n, a(n) for n=1..56.
Stephen D. Cohen, Tim Trudgian, On the least squarefree primitive root modulo p, arXiv:1602.02440 [math.NT], 2016.


EXAMPLE

The primitive roots of 7 less than 7 are 3 and 5. None of them are squareful so 7 is in the sequence.
8 is a primitive root of 11, and 8 is squareful, so 11 is not in the sequence.


MATHEMATICA

selQ[p_] := NoneTrue[PrimitiveRootList[p], #<p && AllTrue[FactorInteger[#], #[[2]] >= 2&]&];
Select[Prime[Range[2, 500]], selQ] (* JeanFrançois Alcover, Sep 28 2018 *)


PROG

(PARI) ar(p) = my(r, pr, j); r=vector(eulerphi(p1)); pr=znprimroot(p); for(i=1, p1, if(gcd(i, p1)==1, r[j++]=lift(pr^i))); vecsort(r) ; \\ from A060749
isok(p) = {my(v = ar(p)); for (i=1, #v, if (ispowerful(v[i]), return(0)); ); 1; }
lista(nn) = forprime(p=1, nn, if (isok(p), print1(p, ", ")));


CROSSREFS

Cf. A001694, A001918, A060749.
Sequence in context: A154320 A173912 A049231 * A092195 A046066 A327819
Adjacent sequences: A268626 A268627 A268628 * A268630 A268631 A268632


KEYWORD

nonn


AUTHOR

Michel Marcus, Feb 09 2016


STATUS

approved



