/*   This program uses recursive functions to find 
the transition curves in Mathieu's equation.  To call it,
type:
                        TC()
*/

tc():=(input(),sign:1,find(),IF n > 0 THEN (sign:-1,find()))$
input():=(n:read("ENTER TRANSITION CURVE NUMBER N"),
      m:read("ENTER DEGREE OF TRUNCATION"))$
find():=(delta:n^2/4,for i thru m do delta:delta+d[i]*e^i,
     print("delta=",delta),print(" "))$
a[j,k]:=IF j < 0 OR k < 0 THEN 0
   ELSE (IF j = 0 AND k = n THEN 1
	     ELSE (IF j = 0 THEN 0
		       ELSE (IF k = n THEN 0
				 ELSE (IF k = 0
					   THEN (-a[j-1,2]/2
					   -sum(d[i]*a[j-i,0],i,1,j))
					   /(n^2/4)
					   ELSE (-(a[j-1,k-2]
					   +a[j-1,k+2]+sign*a[j-1,2-k])
					   /2
					   -sum(d[i]*a[j-i,k],i,1,j))
					   /((n^2-k^2)/4)))))$
d[j]:=IF n = 0 THEN -a[j-1,2]/2
   ELSE -(a[j-1,n-2]+a[j-1,n+2]+sign*a[j-1,2-n])/2$
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