R6:=Matrix([
[6,2,0,2,0,0,0,2,0,0,0,0,0,0],
[6,5,2,0,4,1,1,0,2,4,2,2,0,0],
[0,2,7,2,1,2,2,0,2,0,0,0,0,0],
[0,0,1,4,0,1,1,0,0,0,2,2,3,4],
[0,2,0,0,4,1,1,0,0,0,1,1,6,0],
[0,0,1,1,1,4,0,2,0,2,2,0,0,0],
[0,0,1,1,1,0,4,2,0,2,0,2,0,0],
[0,0,0,0,0,1,1,4,2,0,0,0,0,0],
[0,0,0,0,0,0,0,2,3,0,1,1,0,4],
[0,1,0,0,0,1,1,0,0,4,0,0,0,2],
[0,0,0,1,0,1,0,0,1,0,3,1,0,0],
[0,0,0,1,0,0,1,0,1,0,1,3,0,0],
[0,0,0,0,1,0,0,0,0,0,0,0,3,0],
[0,0,0,0,0,0,0,0,1,0,0,0,0,2]
]);
Nodes
0 : 1 0 3 2 5 4 7 6 9 8 11 10 
1 : 1 0 3 2 5 4 7 6 11 10 9 8 
2 : 1 0 3 2 5 4 11 8 7 10 9 6 
3 : 1 0 3 2 5 4 11 10 9 8 7 6 
4 : 1 0 3 2 7 6 5 4 11 10 9 8 
5 : 1 0 3 2 11 6 5 10 9 8 7 4 
6 : 1 0 3 2 11 8 7 6 5 10 9 4 
7 : 1 0 3 2 11 10 7 6 9 8 5 4 
8 : 1 0 3 2 11 10 9 8 7 6 5 4 
9 : 1 0 5 4 3 2 7 6 11 10 9 8 
10 : 1 0 5 4 3 2 11 10 9 8 7 6 
11 : 1 0 7 6 5 4 3 2 11 10 9 8 
12 : 1 0 11 6 5 4 3 10 9 8 7 2 
13 : 1 0 11 10 9 8 7 6 5 4 3 2