A174621 a(n) is the smallest generator for the group of numbers relatively prime to n under multiplication mod n; a(n) = -1 if n is not a power of a prime or twice a power of a prime.

1, 2, 3, 2, 5, 3, -1, 2, 3, 2, -1, 2, 3, -1, -1, 3, 5, 2, -1, -1, 7, 5, -1, 2, 7, 2, -1, 2, -1, 3, -1, -1, 3, -1, -1, 2, 3, -1, -1, 6, -1, 3, -1, -1, 5, 5, -1, 3, 3, -1, -1, 2, 5, -1, -1, -1, 3, 2, -1, 2, 3, -1, -1, -1, -1, 2, -1, -1, -1, 7, -1, 5, 5, -1, -1, -1, -1, 3, -1, 2, 7, 2, -1, -1, 3, -1, -1, 3, -1, -1, -1, -1, 5, -1, -1, 5, 3, -1, -1

Offset

2,2

Comments

Same as A046145, except for taking -1 instead of 0. - Joerg Arndt, Jan 16 2015

Links

Table of n, a(n) for n=2..100.

Maple

subs(FAIL=-1, [seq(numtheory:-primroot(n), n=2..1000)]); # Robert Israel, Jan 11 2015

Mathematica

lst = {}; f[n_] := PrimitiveRoot[n]; Do[If[IntegerQ@f[n], g = f[n], g = -1]; AppendTo[lst, g], {n, 2, 73}]; Prepend[lst, -1]

Crossrefs

Cf. A046145.

Sequence in context: A046145 A103309 A248207 * A369029 A007967 A054494

Adjacent sequences: A174618 A174619 A174620 * A174622 A174623 A174624

Keyword

easy,sign

Author

Vladimir Joseph Stephan Orlovsky, Mar 23 2010

Extensions

Name changed by Arkadiusz Wesolowski, Jul 19 2012

Offset changed and ambiguous term a(0) removed by Arkadiusz Wesolowski, Jul 20 2012

a(1) removed by Joerg Arndt, Jan 11 2015

Status

approved