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A218005 Nonsquare semiprimes p*q (10 excluded) giving record large smallest number p^r * q^s such that each decimal digit appears a prime number of times. 0
6, 14, 15, 33, 57, 185, 237, 247, 291, 327, 403 (list; graph; refs; listen; history; text; internal format)



The idea for this sequence derives from A216854 and A217404 through A217433. 10 is excluded as a special case, as it necessitates finding the smaller of powers of 2 and 5 to have no digit other than 0 not appearing a prime number of times (to then be multiplied by the first power of 10 to give prime count for this digit). Even the sparser sets of mere prime powers should have members satisfying the criterion; but the numbers can be quite large, and at time of submission the actual record value for this sequence's a(11) (13*31) is unknown. The record values to that point are: (2^56)*(3^12), (2^36)*(7^15), (3^35)*(5^17), (3^29)*(11^22), (3^24)*(19^22), (5^30)*(37^12), (3^48)*(79^9), (13^40)*(19^4), (3^16)*(97^26), and (3^248)*(109^244).


Table of n, a(n) for n=1..11.


Cf. A216854, A217404, A217407, A217410, A217413, A217416, A217419, A217422, A217425, A217428, A217431.

Sequence in context: A107982 A081535 A325698 * A063600 A116926 A140330

Adjacent sequences:  A218002 A218003 A218004 * A218006 A218007 A218008




James G. Merickel, Oct 17 2012



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Last modified October 21 17:14 EDT 2019. Contains 328302 sequences. (Running on oeis4.)