Any large factorial will have a number of zero behind it, and one could write an expression to compute the number of trailing zeros, but how would one go about computing the non-zero end digits?
E.g. compute first 5 non-zero end digits of (10^12)!
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closed as too localized by Igor Rivin, Matthew Daws, Kevin O'Bryant, Felipe Voloch, Emil Jeřábek Nov 9 2011 at 18:18 |
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This will be the least complete answer I've ever posted, but perhaps somebody else will be able to add to it. Not a complete answer (because I don't find any paper online), but I've heard Jean-Marc Deshouillers speak on his (with others, but I don't recall with whom) proof that the last non-zero base-$p$ digit of $n!$ forms a $q$-automatic sequence. I don't recall the hypothesis on $p$, nor the connection between $p$ and $q$. But this answers (to a very limited extent) the real math-research level question hidden in this homework question. Or at least it would, if I could recall any details! |
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