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 A046146 Largest primitive root modulo n, or 0 if no root exists. 13
 0, 0, 1, 2, 3, 3, 5, 5, 0, 5, 7, 8, 0, 11, 5, 0, 0, 14, 11, 15, 0, 0, 19, 21, 0, 23, 19, 23, 0, 27, 0, 24, 0, 0, 31, 0, 0, 35, 33, 0, 0, 35, 0, 34, 0, 0, 43, 45, 0, 47, 47, 0, 0, 51, 47, 0, 0, 0, 55, 56, 0, 59, 55, 0, 0, 0, 0, 63, 0, 0, 0, 69, 0, 68, 69, 0, 0, 0, 0, 77, 0, 77, 75, 80, 0, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS The value 0 at index 0 says 0 has no primitive roots, but the 0 at index 1 says 1 has a primitive root of 0, the only real 0 in the sequence. - Initial terms corrected by Harry J. Smith, Jan 27 2005 a(n) is nonzero if and only if n is 2, 4, or of the form p^k, or 2*p^k where p is an odd prime and k>0. - Tom Edgar, Jun 02 2014 LINKS T. D. Noe, Table of n, a(n) for n = 0..10000 Eric Weisstein's World of Mathematics, Primitive Root. MATHEMATICA f[n_] := Block[{pr = PrimitiveRootList[n]}, If[pr == {}, 0, pr[[-1]]]]; Array[f, 86, 0] (* Robert G. Wilson v, Nov 03 2014 *) PROG (PARI) for(i=0, 100, p=0; for(q=1, i-1, if(gcd(q, i)==1&&znorder(Mod(q, i))==eulerphi(i), p=q)); print1(p", ")) /* V. Raman, Nov 22 2012 */ CROSSREFS Cf. A001918, A046144, A046145, A002233, A071894, A219027, A008330, A010554. Sequence in context: A175108 A265145 A103310 * A081768 A273493 A193404 Adjacent sequences:  A046143 A046144 A046145 * A046147 A046148 A046149 KEYWORD nonn AUTHOR EXTENSIONS Initial terms corrected by Harry J. Smith, Jan 27 2005 STATUS approved

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Last modified February 22 06:24 EST 2020. Contains 332116 sequences. (Running on oeis4.)