### Floor sum

Posted:

**Fri Nov 29, 2019 11:37 am**I've noticed Graham, Knuth (Concrete Mathematics, 2nd ed., p. 86) show how to do sum(floor(sqrt(k)), 0 <= k < n). Did anybody try and tackle sum(floor(sqrt(k (r / 2 - k))), 0 < k < r / 2)? This would actually solve a particular PE problem in closed form.