A(4)=10: the 10 permutations of 4 elements with major index equal to inversion number are
#: perm #inv. inversion table
1: [ 0 1 2 3 ] 0 [ 0 0 0 ]
2: [ 0 3 1 2 ] 2 [ 0 2 0 ]
3: [ 1 0 2 3 ] 1 [ 0 0 1 ]
4: [ 1 2 0 3 ] 2 [ 0 1 1 ]
5: [ 1 2 3 0 ] 3 [ 1 1 1 ]
6: [ 2 1 0 3 ] 3 [ 0 1 2 ]
7: [ 2 1 3 0 ] 4 [ 1 1 2 ]
8: [ 2 3 1 0 ] 5 [ 1 2 2 ]
9: [ 3 0 2 1 ] 4 [ 1 0 3 ]
10: [ 3 2 1 0 ] 6 [ 1 2 3 ]
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