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
Examples
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
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