Prove every number in the sequence 38, 381, 3811, 38111, 381111, ... is composite.
(In reply to
Another way of seeing part of it by Jer)
I perhaps oversimplified the corresponding expression in my last post.
1/9(7*10^n - 1)(7*10^n + 7^2*10^(2n) + 1) =
1/3(7*10^n - 1)*1/3(7*10^n + 7^2*10^(2n) + 1) =
23 | 233 | 2333 | 23333 | 233333 * 1657 | 163567 | 16335667 | 1633356667 | 163333566667
etc.
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Posted by broll
on 2017-06-30 23:14:23 |
re: Another way of seeing part of it
