Floor function

sumfor(n, 1, 100, floor(2#n))==625

Like this

$\sqrt1+ ... \sqrt4+ ...\sqrt9+...\sqrt{16}+...\sqrt{25}+...\sqrt{36}+...\sqrt{49}+...\sqrt{64}+...\sqrt{81}+... \sqrt{100}\\ 3*1 + 5*2 + 7*3 + 9*4 + 11*5 + 13*6 + 15*7 + 17*8 + 19*9 + 10\\ 3+ 10 + 21 + 36 + 55 + 78 + 105 + etc$