Determine the minimum value of a positive base ten integer N, such that each of the last seven digits of N3 is 7 but the eighth digit from the right in N3 is not 7.
(In reply to computer solution
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
This is a pretty efficient way to search. I'm sure a quick program could extend this to many digits.
Posted by Jer
on 2009-06-26 20:32:47