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A122060 Position in decimal expansion of 1/n where repetition begins. 0
2, 3, 2, 4, 3, 3, 7, 5, 2, 3, 3, 4, 7, 8, 3, 6, 17, 3, 19, 4, 7, 4, 23, 5, 4, 8, 4, 11, 29, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

If 1/n = 0.XYYYYY... then sequence gives index of first digit of the second Y.

a(4) = 4 and a(p) = p for primes p = {7, 17, 19, 23, 29, 47, 59, 61, 97, ...} = A001913(n) Cyclic numbers: primes with primitive root 10. - Alexander Adamchuk, Jan 28 2007

LINKS

Table of n, a(n) for n=1..30.

FORMULA

a(n)=A121341(n)+2 if 1/n terminates, else a(n)=A121341(n)+1. - R. J. Mathar, Sep 20 2006

EXAMPLE

a(4) = 4 because in 0.2500 the zero begins repeating at the fourth position.

a(17) = 17 because 0.05882352941176470588... begins repeating at the 17th position.

CROSSREFS

Cf. A001913, A002371.

Sequence in context: A072645 A316714 A135817 * A088939 A324183 A004596

Adjacent sequences:  A122057 A122058 A122059 * A122061 A122062 A122063

KEYWORD

nonn,base

AUTHOR

Ben Paul Thurston, Sep 14 2006

STATUS

approved

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Last modified March 19 18:49 EDT 2019. Contains 321330 sequences. (Running on oeis4.)