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Topic: Origin of the Sub-factorial Notation
Replies: 2   Last Post: Jun 3, 2009 12:14 PM

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Pat Ballew

Posts: 74
Registered: 12/3/04
Origin of the Sub-factorial Notation
Posted: May 31, 2009 1:25 PM
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I'm hoping someone can give me a reference for the use of !n to represent the sub-factorial of n objects.
I know that the term was created by Whitworth, and that he used a symbol |_|__n__ that was a modification of Jarrett's Factorial symbol.

Cajori mentions that G Chrystal used an inverted factorial after the n for the symbol, so I assume the common !n must be after the 1920's.

If you know of a reference or can send a digital image, I would be very grateful,


Pat Ballew
Lakenheath, UK and

Elk Rapids, Michigan

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