I am working my way through Apostol's text on number theory.
Euler's summation formula is given as:
$$ \sum_{y < n \leq x}f(n) = \int_y^x f(t)dt + \int_y^x(t-[t])f'(t)dt + f(x)([x] - x) - f(y)([y] - y) $$
My question is, what is the meaning of the square bracket notation?
$[x]$ should stand for the integer part (or floor function) of $x$.