A061564 Numbers k such that the repeating part of the decimal expansion of 1/k (omitting leading or trailing zeros) forms a prime number.

3, 12, 18, 27, 30, 33, 36, 45, 48, 75, 120, 180, 192, 198, 270, 288, 300, 330, 333, 360, 369, 450, 480, 495, 750, 768, 909, 1152, 1200, 1584, 1800, 1875, 1920, 1980, 1998, 2151, 2304, 2439, 2700, 2880, 2997, 3000, 3072, 3300, 3330, 3333, 3600, 3690, 4500, 4800

Offset

1,1

Links

Table of n, a(n) for n=1..50.

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

Example

1/18 = 0.05555555..., the repeating part is 5, so 18 is in the sequence.
277 is not a term because the repetend of 1/277 is 3610108303249097472924187725631768953068592057761732851985559566787, which is not a prime. - Barry Smyth, Mar 31 2022

Crossrefs

Cf. A036275, A060284.

Sequence in context: A125821 A239052 A063229 * A348169 A342785 A166038

Adjacent sequences: A061561 A061562 A061563 * A061565 A061566 A061567

Keyword

easy,nonn,base

Author

Brian Wallace (wallacebrianedward(AT)yahoo.co.uk), May 18 2001

Extensions

Corrected and extended by Klaus Brockhaus, May 19 2001

More terms from Lior Manor, Nov 26 2001

Incorrect term 277 removed by Barry Smyth, Mar 31 2022

Corrected and extended by Sean A. Irvine, Feb 25 2023

Status

approved