# Does this problem have a name?

Recently our lecturer told us that it is an unsolved mathematical problem if the following while loop aka iteration ever terminates. Unfortunately I forgot to ask him what it is called. If someone recognizes this "problem" I would be glad to know what it is called.

Let $n$ be a natural number (if I remember correctly). Calculate the following.

while (n > 1) {
if (n % 2 == 0) {
n = n/2;
} else {
n = 3 ∗ n + 1;
}
}

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As you will find when you read the Wikipedia article, it has lots of names. –  André Nicolas Feb 4 '13 at 7:07