A007738 Period of repeating digits of 1/n in base 7.

1, 1, 1, 2, 4, 1, 1, 2, 3, 4, 10, 2, 12, 1, 4, 2, 16, 3, 3, 4, 1, 10, 22, 2, 4, 12, 9, 2, 7, 4, 15, 4, 10, 16, 4, 6, 9, 3, 12, 4, 40, 1, 6, 10, 12, 22, 23, 2, 1, 4, 16, 12, 26, 9, 20, 2, 3, 7, 29, 4, 60, 15, 3, 8, 12, 10, 66, 16, 22, 4, 70, 6, 24, 9, 4, 6, 10, 12, 78, 4, 27, 40, 41, 2, 16, 6, 7, 10

Offset: 1

Author

N. J. A. Sloane, Hal Sampson (hals(AT)easynet.com)

Keywords

• nonn
• base

Links

• T. D. Noe, Table of n, a(n) for n=1..1000
• Index entries for sequences related to decimal expansion of 1/n

Programs

Mathematica

f[n_] := MultiplicativeOrder[7, n/(7^IntegerExponent[n, 7])]; Array[f, 80] (* Robert G. Wilson v, Jun 10 2011 *)

PARI

a(n)=znorder(Mod(7,n/7^valuation(n,7))) \\ Charles R Greathouse IV, Jun 10 2011