Group generated by two permutations : groupermu

groupermu takes as argument two permutations a and b.
groupermu returns the group of the permutations generated by a and b.
Input :

groupermu([0,2,1,3],[3,1,2,0])

Output

[[0,2,1,3],[3,1,2,0],[0,1,2,3],[3,2,1,0]]