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From: hopp@nbs-amrf.UUCP (Ted Hopp)
Newsgroups: net.math
Subject: Re: permuting 0123456789
Message-ID: <435@nbs-amrf.UUCP>
Date: Fri, 22-Feb-85 20:51:47 EST
Article-I.D.: nbs-amrf.435
Posted: Fri Feb 22 20:51:47 1985
Date-Received: Wed, 27-Feb-85 03:50:00 EST
References: <201@ihnet.UUCP>, <8414@brl-tgr.ARPA>
Organization: National Bureau of Standards
Lines: 14

> > 	How many permutations of the digits 0-9 have no digits in common

> This should be easy:  How many unrestricted permutations are there?
> How many permutations 0xxxxxxxxx are there?  x1xxxxxxxx?  etc.
> Subtract the latter 10 quantities from the first.  Voila!

Not quite.  You then have to add back all the permutations 01xxxxxxxx,
0x2xxxxxxx, etc. that you counted twice.  Then you have to subtract
back the permutations 012xxxxxxx, 01x3xxxxxx, etc. that you added in
twice. Then you have to ....

-- 

Ted Hopp	{seismo,umcp-cs}!nbs-amrf!hopp