[seqfan] when is 1234...n a prime?

Neil Sloane njasloane at gmail.com
Wed Sep 30 03:18:15 CEST 2015


To Seq Fans:

Consider the sequence with nth term equal to the
concatenation of the decimal numbers 1234...n (https://oeis.org/A007908).
When is the first prime? The comments in A007908 say
that there should be infinitely many primes, and that there
are no primes among the first 64000 terms.
If you would like to help with this search, you could leave a comment
in A007908 saying that there are no primes among terms X through Y,
or, of course, that n = Z gives a (probable) prime, which would be
pretty exciting.


Best regards
Neil

Neil J. A. Sloane, President, OEIS Foundation.
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Phone: 732 828 6098; home page: http://NeilSloane.com
Email: njasloane at gmail.com


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