I've read in somewhere that $\displaystyle f_{n} = 2^{2^{n}}+1$ is never prime for all integers $\displaystyle n>4$. How can that be proven?

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- Mar 6th 2010, 10:17 PMVancesComposite numbers
I've read in somewhere that $\displaystyle f_{n} = 2^{2^{n}}+1$ is never prime for all integers $\displaystyle n>4$. How can that be proven?

- Mar 6th 2010, 11:44 PMTwistedOne151
Whether there are any Fermat numbers $\displaystyle F_n$, n>4, that are prime is an unsolved question in mathematics; see here.

--Kevin C.