Number of conjugacy classes of subgroups of index n in free group of rank 4.

A057007

Number of conjugacy classes of subgroups of index n in free group of rank 4.

Terms

    a(0) =1a(1) =15a(2) =235a(3) =14120a(4) =1712845a(5) =371515454a(6) =127635996839

External references