n can be 47 or 17.
Suppose n2+32n+8=m2 where m is a positive integer. Note that this can be rewritten as (n+16)2−248=m2, which implies
(n+m+16)(n−m+16)=248=23×31.
Hence, (n+m+16,n−m+16)=(248,1),(124,2),(62,4),(31,8). For each pair, we can solve the system of two linear equations in two unknowns. The only positive integer solutions are (n,m)=(47,61),(17,29).