The exponent rule for raising a power to a power indicates that we can multiply the exponents. So, A^$n^2+3$ can be simplified to A^n^$2+3$ which equals A^n^5.

Similarly, simplifying a^$6n+n^2$ we get a^$n^2+6n$.

Therefore, A^$n^2+3$ can be rewritten as A^n^5 and a^$6n+n^2$ can be rewritten as a^$n^2+6n$.