Tables again                  T2
   a =. i.n =. 5
   bump =. +&1
   a */ a
0 0 0  0  0
0 1 2  3  4
0 2 4  6  8
0 3 6  9 12
0 4 8 12 16
   
   n | */~ a
0 0 0 0 0
0 1 2 3 4
0 2 4 1 3
0 3 1 4 2
0 4 3 2 1
   
   bump 4| +/~ i. 4 
1 2 3 4
2 3 4 1
3 4 1 2
4 1 2 3
