(* pl6.m:  S. A. Fulling, Nov. 1995 (first version summer 1994) *)

Off[General::spell1]
Share[];
orderRules = {
   x1^(n1_)*x2^(n2_) :> x1^n2*x2^n1 /; n2 > n1,
   x1^(n1_)*x3^(n3_) :> x1^n3*x3^n1 /; n3 > n1,
   x2^(n2_)*x3^(n3_) :> x2^n3*x3^n2 /; n3 > n2,
   x1^(n1_)*x4^(n4_) :> x1^n4*x4^n1 /; n4 > n1,
   x2^(n2_)*x4^(n4_) :> x2^n4*x4^n2 /; n4 > n2,
   x3^(n3_)*x4^(n4_) :> x3^n4*x4^n3 /; n4 > n3,
   x1^(n1_)*x5^(n5_) :> x1^n5*x5^n1 /; n5 > n1,
   x2^(n2_)*x5^(n5_) :> x2^n5*x5^n2 /; n5 > n2,
   x3^(n3_)*x5^(n5_) :> x3^n5*x5^n3 /; n5 > n3,
   x4^(n4_)*x5^(n5_) :> x4^n5*x5^n4 /; n5 > n4,
   x1^(n1_)*x6^(n6_) :> x1^n6*x6^n1 /; n6 > n1,
   x2^(n2_)*x6^(n6_) :> x2^n6*x6^n2 /; n6 > n2,
   x3^(n3_)*x6^(n6_) :> x3^n6*x6^n3 /; n6 > n3,
   x4^(n4_)*x6^(n6_) :> x4^n6*x6^n4 /; n6 > n4,
   x5^(n5_)*x6^(n6_) :> x5^n6*x6^n5 /; n6 > n5
   };

qmax = 5  
max = 2(qmax+1)

link12 = Sum[t^(2j) c[j] x1^j x2^j, {j, 0, qmax}] + O[t]^max
link13 = link12 /. x2->x3;
link23 = link13 /. x1->x2;
link14 = link12 /. x2->x4;
link24 = link14 /. x1->x2;
link34 = link14 /. x1->x3;
link15 = link12 /. x2->x5;
link25 = link15 /. x1->x2;
link35 = link15 /. x1->x3;
link45 = link15 /. x1->x4;
link16 = link12 /. x2->x6;
link26 = link16 /. x1->x2;
link36 = link16 /. x1->x3;
link46 = link16 /. x1->x4;
link56 = link16 /. x1->x5;
point1 = Sum[t^(2j) c[j] x1^(2j), {j, 0, qmax}] + O[t]^max
point2 = point1 /. x1 -> x2;
point3 = point1 /. x1 -> x3;
point4 = point1 /. x1 -> x4;
point5 = point1 /. x1 -> x5;
point6 = point1 /. x1 -> x6; 

identity = link12*link13*link23*link14*link24*link34*link15*link25*link35*
     link45*link16*link26*link36*link46*link56*
     point1*point2*point3*point4*point5*point6;
pl6temp = (Expand[Normal[identity] * x1^2 x2^2 x3^2 x4^2 x5^2 x6^2] //.
                             orderRules)/(x1^2 x2^2 x3^2 x4^2 x5^2 x6^2);
pl6 = Collect[pl6temp, Prepend[Table[c[qmax-i], {i,0,qmax}], t]]

pl6point = pl6 //. c[n_] -> 1
pl6line = pl6 //. {x1->1, x2->1, x3->1, x4->1, x5->1, x6->1}
pl6total = pl6line //. c[n_] -> 1

Save["pl6.out", pl6, pl6point, pl6line, pl6total]
Quit[]