A072989 Numbers m>0 such that the number of solutions to x^m==1 (mod m), 1<=x<=m, is not equal to gcd(m, phi(m)).

20, 30, 40, 42, 52, 60, 66, 68, 70, 78, 80, 84, 90, 100, 102, 104, 110, 114, 116, 120, 126, 130, 132, 136, 138, 140, 148, 150, 154, 156, 160, 164, 168, 170, 171, 174, 180, 182, 186, 190, 198, 200, 204, 208, 210, 212, 220, 222, 228, 230, 232, 234, 238, 240

Offset

1,1

Comments

Conjecture: limit of a(n)/n is zero.

This conjecture is certainly wrong as stated, because sequences "Numbers such that..." have lim a(n)/n >= 1 and a(n) > n for all indices following the first one for which this holds, as here: a(1) > 1. - M. F. Hasler, Feb 24 2014

Links

Robert G. Wilson v, Table of n, a(n) for n = 1..220

Formula

Equals { m>0 | A009195(m) != A072994(m) }. - M. F. Hasler, Feb 23 2014

Prog

(PARI) isok(m) = sum(x=1, m, Mod(x, m)^m==1) != gcd(m, eulerphi(m)); \\ Michel Marcus, Feb 18 2021

Crossrefs

Cf. A009195, A072994.

Sequence in context: A029721 A224400 A132067 * A216603 A166730 A109944

Adjacent sequences: A072986 A072987 A072988 * A072990 A072991 A072992

Keyword

easy,nonn

Author

Benoit Cloitre, Aug 21 2002

Status

approved