A338792 a(n) is the least number k such that 1/prime(k) has repeating decimal expansion of period n.

1, 2, 5, 12, 26, 13, 4, 52, 21, 28693, 1128, 2431, 1221, 16, 71954, 11, 7, 153888, 8, 27417323062119920, 496, 14, 9, 223378173194137397198, 5760923, 2403, 149, 134, 10, 452, 47, 406, 71, 19, 27, 20, 37607875619, 150886, 22544062111497849

Offset

0,2

Links

Table of n, a(n) for n=0..38.

Index entries for sequences related to decimal expansion of 1/n

Formula

a(0) = 1; a(n) = A000720(A007138(n)).

Example

1/prime(1)  = 1/2  = 0.5 (finite decimal expansion).
1/prime(2)  = 1/3  = 0.3(3)... (period 1).
1/prime(5)  = 1/11 = 0.09(09)... (period 2).
1/prime(12) = 1/37 = 0.027(027)... (period 3).

Crossrefs

Cf. A000720, A002371, A003060, A007138.

Sequence in context: A117177 A287141 A214610 * A221720 A258099 A132977

Adjacent sequences: A338789 A338790 A338791 * A338793 A338794 A338795

Keyword

nonn,base

Author

Ilya Gutkovskiy, Nov 09 2020

Extensions

a(19)-a(38) from Daniel Suteu, Nov 09 2020 [using data from A007138 and A234317]

Status

approved