Number of two-element generating sets in the symmetric group S_n.

A001691

Number of two-element generating sets in the symmetric group S_n.

Terms

    a(0) =0a(1) =1a(2) =9a(3) =108a(4) =3420a(5) =114480a(6) =7786800a(7) =497266560a(8) =42616445760

External references