Always composite?

[Alhazen]

a is a positive integer>1

Let k=a^(a+1)+(a+1)^a

Examples :

k=2^3+3^2=8+9=17 is prime
k=3^4+4^3=145 is composite

If a>2 k is it always composite ?

If yes can we prove it?

Thank you for any comment.

[Lord_Farin]

k = 80, 342 and 848 yield primes (at least, that's what Mathematica says).

[Alhazen]

k = 80, 342 and 848 yield primes (at least, that's what Mathematica says).

Thank you very much.
You helped me to find the list in Sloane

https://oeis.org/search?q=2%2C80%2C342% ... &go=Search

A073499 as a simple table:
n a(n)
1 1
2 2
3 80
4 342
5 848
6 1194
7 2658
8 4790
9 9376

What is strange is that all are even.
Is that means that if k is odd then there will be no prime of such form?
Thank you.
There is maybe some secret to discover here