# 5n+n5^n+n is never prime?

In the comments to the question: If $(a^{n}+n ) \mid (b^{n}+n)$ for all $n$, then $a=b$, there was a claim that $5^n+n$ is never prime (for integer $n>0$).

It does not look obvious to prove, nor have I found a counterexample.

Is this really true?

Update: $5^{7954} + 7954$ has been found to be prime by a computer: http://www.mersenneforum.org/showpost.php?p=233370&postcount=46

Thanks to Douglas (and lavalamp)!

Running WinPFGW (it should be available from the primeform yahoo group http://tech.groups.yahoo.com/group/primeform/), it found that $5^n+n$ is 3-probable prime when n=7954. Moreover, for every n less than 7954, we have $5^n+n$ is composite.
To actually certify that $5^{7954}+7954$ is a prime, you could use Primo (available from http://www.ellipsa.eu/public/misc/downloads.html). I’ve begun running it (so it’s passed a few more pseudo-primality tests), but I doubt I will continue until it’s completed — it could take a long time (e.g. a few months).
EDIT: $5^{7954}+7954$ is officially prime. A proof certificate was given by lavalamp at mersenneforum.org.