A231773 - OEIS

A231773

Numbers k such that there are no numbers with k primitive roots.

3, 5, 7, 9, 11, 13, 14, 15, 17, 19, 21, 23, 25, 26, 27, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 45, 46, 47, 49, 50, 51, 53, 55, 56, 57, 58, 59, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 78, 79, 81, 83, 85, 86, 87, 89, 90, 91, 93, 94, 95

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OFFSET

1,1

COMMENTS

Numbers k such that A231772(k) = 0.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A007617(n) for n <= 16.

PROG

(PARI) r=95; for(n=2, r, m=0; for(c=2*n+1, n^2+1, if(n%2==1, break); e=eulerphi(c); if(e==lcm(znstar(c)[2])&&eulerphi(e)==n, m=1; break)); if(m==0, print1(n, ", ")));

CROSSREFS

Cf. A007617, A010554, A046144, A231772.

Sequence in context: A097218 A196546 A371179 * A007617 A065878 A186383

Adjacent sequences: A231770 A231771 A231772 * A231774 A231775 A231776

KEYWORD

nonn

AUTHOR

Arkadiusz Wesolowski, Nov 13 2013

STATUS

approved