>>753
J^n=[[3^n,n*3^(n-1),0][0,3^n,0],[0,0,5^n]]

exp(tJ)
= Σ[n=0,∞](tJ)^n/n!
=[[e^(3t),te^(3t),0][0,e^(3t),0],[0,0,e^(5t)]]