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Alphabet consists of M letters. Strings may have repeats.

The question is: how many strings of n letters are there such that every string differs from each other by m or more letters?

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Can I ask if you've checked the many other similar questions on the site first? – Simon Hayward Dec 9 '12 at 15:41
Certainly I have. Yet I've found nothing similar enough to be useful: I just have too little knowledge in combinatorics to transform them into my case. If a question which describes the same problem in a different manner was already asked and I have missed it, I would appreciate if you point to it. – Allis Tauri Dec 9 '12 at 15:53

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