pfffffffftttttttttttt i waited 1 whole hour before giving up
this loop is almost infinite
i got this code...

Code:
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        'n → n/2 (n is even)
        'n → 3n + 1 (n is odd)
        Dim n As Long, ChainLength As Integer, LargestChain As Integer
        LargestChain = 0
        For n = 1 To 1000000
            ChainLength = 0
            Do Until n = 1
                If n Mod 2 = 0 Then
                    n = n / 2
                    ChainLength = ChainLength + 1
                Else
                    n = 3 * n + 1
                    ChainLength = ChainLength + 1
                End If
            Loop
            If ChainLength > LargestChain Then LargestChain = ChainLength
        Next
        TextBox1.Text = LargestChain
        TextBox2.Text = n
    End Sub
The question is the following:
The following iterative sequence is defined for the set of positive integers:

n → n/2 (n is even)
n → 3n + 1 (n is odd)

Using the rule above and starting with 13, we generate the following sequence:


13 → 40 → 20 → 10 → 5 → 16 → 8 → 4 → 2 → 1

It can be seen that this sequence (starting at 13 and finishing at 1) contains 10 terms. Although it has not been proved yet (Collatz Problem), it is thought that all starting numbers finish at 1.

Which starting number, under one million, produces the longest chain?

NOTE: Once the chain starts the terms are allowed to go above one million.