Fibonacci sequence is defined by f(1)=1,f(2)=1 and f(m) =f(m-1)+f(m-2)
i.e. 1, 1, 2, 3, 5, 8, 13, ...

Prove that for all composite values of n>4, f(n) is composite.

(In reply to

Observation by ed bottemiller)

There are 2 theorems concerning prime/composite relation

between Fibo series members and their indices.

You write: **..."Neither is asserting that if n is prime, then F(n) must be prime "** to which I'd like to add **"and vice versa**."

I believe one can EITHER find the proofs on the WEB OR work it out independently OR both.