Sum of powers

$$f(k) = \sum_{r=1}^{n} r^k$$. Find an integer $$x$$ that solves the equation $$f(x) = \bigl(f(1)\bigr)^2$$.

[SOLVED]

1 comment

Prunthaban Kanthakumar solved this puzzle:

$$3$$ from what I learnt in school.

Credit

This is an original puzzle from cotpi.