Do there exists two positive integers and such that is an integer other than the trivial case?
Every natural number can be written as . More specifically for each number , is the n-th element of this sequence, and is the n-th term of this sequence.
Let us first have a look at . If you take a consecutive subset, from index to , the maximum always appears ones.
Proof:
Assume the maximum appears at least twice. As the index of the number has to be of the form , the two appearances can be assumed to be and with and odd and . As , and both ends are in the consecutive subset, $ 2^y (a+1)$ has to be in the subset. But as is odd, is even, and such can be written as with k nonzero and odd. Hence, , so there exists a value larger than for the exponent, so was not the maximum, which leads to a contradiction.
Now, take the sum . By the previous lemma, there is one single element that contains the largest power of two, if written like . Remove that element from the sum. The sum of all other elements can be written as with an integer and the least common multiple of all denominators. As all of the denominators have a lower exponent for two than , is not a multiple of . Let us write this is with
Our total sum is now
As the denominator is a multiple of and the numerator is not, this can never be an integer. QED