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Suppose you listed all primes, with three digits or less, using the digits in this number (1,8, and 9), without limiting the number of times a number can use each digit (i.e., it may have two nines). If they are now listed from least to greatest with signs in the order "+, +, -,", beginning with 11+18+19-181+191+199-811... the sum is 1381, which is a prime as well. [Meiburg]

 

  Submitted: 2009-07-10 10:51:34;   Last Modified: 2009-07-10 18:27:33.



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