Numbers n (relatively prime to 10) such that the decimal form of the period of 1/n is prime.
3, 27, 33, 333, 369, 909, 2151, 2439, 2997, 3333, 27027, 33333, 37683, 41841
2 seqfan posts
Fri Nov 19 00:11:51 CET 2010 [seqfan] Re: extending A179192 (periods of 1/n)