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 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Stephen D. Cohen, Tim Trudgian, On the least square-free 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], #

= 2&]&]; Select[Prime[Range[2, 500]], selQ] (* Jean-François Alcover, Sep 28 2018 *) PROG (PARI) ar(p) = my(r, pr, j); r=vector(eulerphi(p-1)); pr=znprimroot(p); for(i=1, p-1, if(gcd(i, p-1)==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

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Last modified June 4 07:59 EDT 2020. Contains 334822 sequences. (Running on oeis4.)