The question as I see it is to show Sum(1/x), x=1 to n is never an integer. Well, take an example: Sum(1/x) x=1 to x=10 = 7381/2520. The factors of 7381 are 11^2x61, while the factors of 2520 are
2^3x3^2x5x7, so it can not be an integer.
From this example, you can proceed to find a general reason.