FUNCTION :  cuspwid1 - cusp width in Gamma[1](N)

CALLING SEQUENCE :  cuspwid1(a,c,N)                                          
                    

PARAMETERS :     a,c,N - integers where N>0 and (a,c)=1

SYNOPSIS :   Returns the width of the cusp a/c                     
             for the group Gamma[1](N).    
   
EXAMPLES :   

> with(thetaids):
> cuspwid1(1,3,6);
                                       2

> cw12:=cuspmake1(6);                  
                   cw12 := {[0, 1], [1, 0], [1, 2], [1, 3]}

> nc12:=nops(cw12);        
                                   nc12 := 4

> for j from 1 to nc12 do
>   CL:=cw12[j]:
>   a:=CL[1]: c:=CL[2]:
>   if c<>0 then cusp:=a/c: else cusp:=oo: fi:
> printf("%a           %a\n",cusp,cuspwid1(a,c,6));
> od:

0           6
oo           1
1/2           3
1/3           2

> CUSPSANDWIDMAKE1(6);
                       [[oo, 0, 1/2, 1/3], [1, 6, 3, 2]]

> 


DISCUSSION :

We see that the cusp 1/3 has width 2 in GAMMA[1](6).
There are 4 cusps in GAMMA[1](6):

cusp        width
 0           6
oo           1
1/2          3
1/3          2

This agrees with the result using CUSPSANDWIDMAKE1.

SEE ALSO :  

cuspmake1,
CUSPSANDWIDMAKE1