1: AAAAA <=> AAMMM
2: AAAAA <=> AAMMN
3: AAAAA <=> AAMMU
4: AAAAA <=> AAMNM
5: AAAAA <=> AAMNN
.... # many lines deleted
917168: UUUUU <=> UUNMM
917169: UUUUU <=> UUNMN
917170: UUUUU <=> UUNNA
917171: UUUUU <=> UUNNM
917172: UUUUU <=> UUNNN

917172 pairs with minimum difference of 3 from a set of 4 characters taken 5 at a time.