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Origin of the Subfactorial Notation
Posted:
May 31, 2009 1:25 PM


I'm hoping someone can give me a reference for the use of !n to represent the subfactorial 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,
Thanks
Pat Ballew Lakenheath, UK and
Elk Rapids, Michigan



