func mertensNumbers(max) {
    let mertens = Array.Empty(max + 1, 1)
    for n in 2..max {
        for k in 2..n {
            mertens[n] -= mertens[n / k]
        }
    }
    mertens
}

let max = 1000
let mertens = mertensNumbers(max)

let count = 200
let columns = 20
print("First \(count - 1) Mertens numbers:")

for i in 0..<count {
    if i % columns > 0 {
        print(" ", terminator: "")
    }
    print(i == 0 ? "   " : mertens[i].ToString().PadLeft(2, ' ') + " ", terminator: "")
    if (i + 1) % columns == 0 {
        print()
    }
}

var (zero, cross, previous) = (0, 0, 0)
for i in 1..max {
    let m = mertens[i]
    if m == 0 {
        zero += 1
        if previous != 0 {
            cross += 1
        }
    }
    previous = m
}

print("M(n) is zero \(zero) times for 1 <= n <= \(max).")
print("M(n) crosses zero \(cross) times for 1 <= n <= \(max).")