Project Euler Solutions

[Iceglade]

Code:

a = set(range(2,n+1))
    l = round(n**0.5)
    for i in range(2,int(l+1)):
        if i in a:
            s = i**2
            while s <= n:
                if s in a:
                    a.remove(s)
                s += i
    return list(a)

This is O(sqrt n) if I'm not mistaken.