n!+1 is composite.
Last edited by rmpatel5; September 23rd 2008 at 07:21 PM.
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Hint given by book: use Wilson's theorem to guarantee that n!+1 has a prime factor for an appropriately chosen n
Let then .
Thus, is a prime divisor.
Originally Posted by ThePerfectHacker Let then .
Thus, is a prime divisor. would n! -1 be the same thing setting n=p-1 and getting (p-1)!-1 but since 1 is the only inverse modulo of itself it is the same thing as (p-1)!+1??
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