.
For your info :
(a)   a^n   means  
,  and is used ONLY for this purpose: to show raising in degree "n".
      For example,  2^2 = 
 = 4;   3^2 = 
 = 9.
(b)   If you want to show the n-th term of a progression / (of a sequence), write  a[n]  or  a(n). 
      We, the tutors, will read it as  
.