FUNCTION :  qseries[etaq] - Dedekind eta product
    
CALLING SEQUENCE :  etaq(q,a,T)
    
PARAMETERS :   q    - variable
               a,T  - positive integers 
   
SYNOPSIS :   
   
                                                  T
 etaq(q,a,T) returns the q-series expansion to O(q )   
 of the eta-product  
   
   a   a   
 (q , q )  
         oo  
   
 where is real or complex variable (with |q|<1) and  
 a is a positive integer. 
 The series is computed using Euler's pentagonal number theorem. 
   
EXAMPLES :   
   
> etaq(q,2,100);   
   
             80    52    30    14    4        2    10    24    44    70   
          - q   + q   - q   + q   - q  + 1 - q  + q   - q   + q   - q   
----------------------------------------------------------------------------   
> series(%,q,100);   
   
                2    4    10    14    24    30    44    52    70    80   
           1 - q  - q  + q   + q   - q   - q   + q   + q   - q   - q   
----------------------------------------------------------------------------
SEE  ALSO :