The number of unordered pairs (f,g) of functions from {1..n} to itself such that fg=gf (i.e., f(g(i))=g(f(i)) for all i) where f and g are distinct.

A254570

The number of unordered pairs (f,g) of functions from {1..n} to itself such that fg=gf (i.e., f(g(i))=g(f(i)) for all i) where f and g are distinct.

Terms

    a(0) =0a(1) =3a(2) =57a(3) =1284a(4) =34220a(5) =1098720a(6) =41579328a(7) =1832244288a(8) =92830006368

External references