See https://oeis.org/A001175, one of the oldest entries in the OEIS. If your observations aren't mentioned there, please add them! 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@gmail.com On Sun, Jan 24, 2016 at 12:10 PM, Warren D Smith <warren.wds@gmail.com> wrote:
If we merely ask that period>=5*n, that happens for n=10,50,250,1250,6250,31250, and which all are of form 2*5^k, but for no other n up to 270000. Note in particular that n=156250=2*5^7 is NOT listed. In all six of these cases, the period equals 6*n.
--that's funny. Rerunning my program, this time it said n=156250 obeyed the rule (?hardware bug?), and indeed it claims the rule works for each n=2*5^k for k=1,2,3,4,5,6,7,8,9,10,11.
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