pabloferz

#==============================================================================#
# Optimized Sieve of Atkin
#==============================================================================#

function atkin(n::Int)
    s = zeros(Bool, n < 2 ? 0 : n)
    n < 2 && return s; s[2] = true
    n < 3 && return s; s[3] = true
    for x = 1:floor(Int,sqrt(n/4))
        j = 4 * x * x