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Old 2020-09-30, 14:17   #2
R. Gerbicz
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"Robert Gerbicz"
Oct 2005

22·5·73 Posts

Originally Posted by enzocreti View Post
How to proof that numbers of the form 18, 108, 1008, 10008, 100008, 1000...0008 will never be divisible by 6^4?
For n>3 the
a(n)=10^n+8==8 mod 16 hence it won't be divisible by even 16=2^4 so not by 6^4.
And you can check the n<=3 cases easily since 6^4=1296>1008.
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