A171928 Numbers k which divide the periodic part of the decimal expansion of 1/k.

3, 6, 487, 1461, 4383, 13149, 56598313, 169794939

Offset: 1

Author

Zhining Yang, Jan 05 2010

Keywords

• nonn
• base
• more

Comments

There are two definitions of the periodic part: zeros may either begin or end the periodic part. For example, for 1/11 = 0.0909090..., the periodic part could be either 09 or 90. This sequence assumes that the zeros are at the beginning of the periodic part. See A179267 for the case of zeros at the end of the periodic part. The prime numbers in this sequence are in A045616. The three numbers following 487 are 3*487, 9*487, and 27*487. There are no other multiples of 487 here because 3 and 487 are the only prime factors of 10^486-1 that occur to a power greater than 1. - T. D. Noe, Jul 06 2010

Examples

			6 is a term because 1/6 = 0.166666... has periodic part 6, which is divisible by 6.
		

Links

• Helmut Richter, Factors of 10^486-1

Crossrefs

Cf. A045616, A179267.

Extensions

Example shortened by T. D. Noe, Jun 27 2010

Extended by T. D. Noe, Jul 06 2010