It's well known that the numbers of the form $n!\pm1$ are not always prime. Indeed, [Wilson's Theorem](http://en.wikipedia.org/wiki/Wilson%27s_theorem) guarantees that $(p-2)!-1$ and $(p-1)!+1$ are composite for every prime number $p > 5$. > Is there a proof, preferably an elementary proof, that there are infinitely many composite *pairs* of the form $n!\pm1$? The motivation for this question comes from my answer to [this recent question](https://mathoverflow.net/questions/30064/are-the-types-of-nonstandard-natural-numbers-within-a-z-chain-identical). There, I show that every nonstandard model of Peano Arithmetic has a $\mathbb{Z}$-chain consisting entirely of composite numbers. The example I gave is that of a $\mathbb{Z}$-chain contained in the infinite interval $[N!+2,N!+N]$, where $N$ is any nonstandard natural number. I wonder if I could have picked some $\mathbb{Z}$-chain centered at $N!$ instead. A positive answer to the above question would mean that this is indeed possible. Note that it is important in this context that the proof is elementary, but I will also accept beautiful analytic arguments. Andrey Rekalo pointed out that $(N!)^3 \pm 1$ are both composite. This means that, if $N$ is a nonstandard integer, then the $\mathbb{Z}$-chain centered at $(N!)^3$ has only composite numbers all but two have standard factors. I don't know if it's possible to find a $\mathbb{Z}$-chain all of whose elements have a standard factor.