# Composite numbers

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• March 6th 2010, 10:17 PM
Vances
Composite numbers
I've read in somewhere that $f_{n} = 2^{2^{n}}+1$ is never prime for all integers $n>4$. How can that be proven?
• March 6th 2010, 11:44 PM
TwistedOne151
Whether there are any Fermat numbers $F_n$, n>4, that are prime is an unsolved question in mathematics; see here.

--Kevin C.