What decimal digit occurs most often in the sequence of factorials from 77777! to 77877! inclusive?

This can be solved by logic. You do not need to compute any factorials.

Many zeros have built up at the end of 77777! and every fifth one after that adds another. There are more than 15,000 excess zeros in each of these factorials not counting the ones that are mixed in with the non-zeros that probably occur with equal frequency as other digits.

Posted by Charlie on 2024-05-29 10:38:59