Determine the minimum value of a positive base ten integer N, such that each of the last seven digits of N^{3} is 7 but the eighth digit from the right in N^{3} is not 7.
(In reply to
computer solution by Charlie)
I had tried to build this number up from one 7. The problem was on my calculator I ran out of digits at 5 and didn't see a pattern to continue.
3^3 ends in 7
of a3, 53^3 ends in 77
of a53, 753 ends in 777
etc.
This is a pretty efficient way to search. I'm sure a quick program could extend this to many digits.

Posted by Jer
on 20090626 20:32:47 