A070682 Smallest m in range 1..phi(2n+1) such that 10^m == 1 mod 2n+1, or 0 if no such number exists.

0, 1, 0, 6, 1, 2, 6, 0, 16, 18, 6, 22, 0, 3, 28, 15, 2, 0, 3, 6, 5, 21, 0, 46, 42, 16, 13, 0, 18, 58, 60, 6, 0, 33, 22, 35, 8, 0, 6, 13, 9, 41, 0, 28, 44, 6, 15, 0, 96, 2, 4, 34, 0, 53, 108, 3, 112, 0, 6, 48, 22, 5, 0, 42, 21, 130, 18, 0, 8, 46, 46, 6, 0, 42, 148

Offset: 0

Author

N. J. A. Sloane and Amarnath Murthy, May 08 2002

Keywords

• nonn

Crossrefs

Cf. A070667-A070675, A002326, A070676, A053447, A070677, A070678, A053451, A070679, A070681, A070680, A070683.

Programs

PARI

a(n) = {for (m = 1, eulerphi(2*n+1), if (10^m % (2*n+1) == 1, return (m));); return (0);} \\ Michel Marcus, Sep 14 2013