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91 is composite, 9901 is prime, 999001 is composite, 99990001 is prime, 9999900001 is composite, 999999000001 is prime, 99999990000001 is composite, 9999999900000001 is prime. Unfortunately, the next two terms in this sequence are each composite. [Beiler] The greatest prime factor of any 48digit repdigit is 9999999900000001. [Green] 9999999900000001 is the 8th known prime, p, such that (p)^{2} divides (p)_{3}. Can you find other cases like this? [Green] 9999999900000001 = 99999999^2 + 99999999^1 + 99999999^0. [Nwamba]
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