--- In

primenumbers@yahoogroups.com, "David Broadhurst" <d.broadhurst@...> wrote:

>

> > For which n>1 is 4*n!^8 + 1 prime ??

>

> For none. Proof: Set x = (n!)^2 in the identity

> 4*x^4 + 1 = (2*x^2 + 1)^2 - (2*x)^2

Right... of course! Bad example - that's not what I meant to say.

Maybe,

Is 8*n!^8+1 composite for all n>4 ?

Probably not. Actually I don't mind at all. It was just to express the same "Moral" given elsewhere more explicitely. But I should have chosen my example more carefully...

At least this shows that the "32" is in some sense simply the 3rd possibiliy, after 2 and 8. For 2^7 there happen to be 3 small primes; for 2^9 and 2^11 only two. Thus, whenever the first prime is found for 2^5, then the same post can be made replacing 32 with 2^13.)

Maximilian