**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*

Index of A-numbers in seqfan: by ascending order by month by frequency by keyword

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