let isqrt n =
    let rec iter t =
        let d = n - t*t
        if (0 <= d) && (d < t+t+1) // t*t <= n < (t+1)*(t+1)
        then t else iter ((t+(n/t))/2)
    iter 1

let rec gcd a b =
    let t = a % b
    if t = 0 then b else gcd b t

let coprime a b = gcd a b = 1

let num_to ms =
    let mutable ctr = 0
    let mutable prim_ctr = 0
    let max_m = isqrt (ms/2)
    for m = 2 to max_m do
        for j = 0 to (m/2) - 1 do
            let n = m-(2*j+1)
            if coprime m n then
                let s = 2*m*(m+n)
                if s <= ms then
                    ctr <- ctr + (ms/s)
                    prim_ctr <- prim_ctr + 1
    (ctr, prim_ctr)

let show i =
    let s, p = num_to i in
    printfn "For perimeters up to %d there are %d total and %d primitive" i s p;;

List.iter show [ 100; 1000; 10000; 100000; 1000000; 10000000; 100000000 ]