Create the convolution-power vector from initial vector x and power n. In other words, similar to the scalar case, raising to the n-th power means repeating the convolution on itself n times.

Assume that n is a non-negative integer and x is a row vector.

Examples:

 convpower(1:5,0)
 ans =
     1

 convpower(1:5,1)
 ans = 
     1     2     3     4     5

 convpower(1:5,2)
 ans = 
     1     4    10    20    35    44    46    40    25

Neither string operations nor interpolations are allowed!