The divisibility of an-bn by powers of n
Abstract
For given integers a,b, and j at least 1 we determine the set of integers n for which an-bn is divisible by nj. For j=1,2, this set is usually infinite; we find explicitly the exceptional cases for which a,b the set is finite. For j=2, we use Zsigmondy's Theorem for this. For j at least 3 and gcd(a,b)=1, the set is probably always finite; this seems difficult to prove, however. We also show that determination of the set of integers n for which an+bn is divisible by nj can be reduced to that of the above set.
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