FUNCTION :  qseries[findlincombomodp] - tries to express a q-series as a 
                                        linear combination mod p of 
                                        a given list of q-series.

CALLING SEQUENCE :  findlincombomodp(f,L,SL,p,q,topshift)


PARAMETERS :   L   - list of q-series
               SL  - list of names
               p   - prime              
               q   - variable           
               topshift - integer greater than -20      

GLOBAL VARIABLES : ct, gooo

SYNOPSIS :   
   
findlincombomodp(f,L,SL,p,q,topshift) returns a set of potential 
set of linear combinations mod p from L for the given q-series f.
The value of topshift is usually taken to be zero. However if
it appears that spurious relations are being generated then a higher
value of topshift should be taken.

SL is a list of names used in printing the linear combinbations.

NOTE: The global var ct is tranpose of matrix of coeffs.
      The global var gooo is its Nullspace mod p. These used for debugging
      purposes. This function is a mod p version of findlincombo

EXAMPLES :   


 > E4:=1+240*add(n^3*q^n/(1-q^n),n=1..300):
 > E6:=1-504*add(n^5*q^n/(1-q^n),n=1..300):
 > P:=series(1/etaq(q,1,300),q,300):       
 > ETA1:=etaq(q,1,300):
 > F1:=sift(E4^16*E6*P,q,13,6,299):
 > BB13:=[seq(ETA1^11*E6*E4^(3*j+1),j=0..5)]:
 > SBB13:=[seq(_ETA1^11*_E6*_E4^(3*j+1),j=0..5)]:
 > findlincombomodp(F1,BB13,SBB13,13,q,-8);
                                             nx = , 6
 
                                         # of terms , 19
 
                                                11
                                        -6 _ETA1   _E6 _E4
 
 

DISCUSSION :

We see that F1 is a linear combination of functions in BB13 mod 13.

SEE  ALSO :  findhom, findhomcombo, findhomcombomodp, findlincombo