Number of labeled plane 2-trees with n nodes.

A003092

Number of labeled plane 2-trees with n nodes.

Terms

    a(0) =0a(1) =1a(2) =2a(3) =36a(4) =1200a(5) =57000a(6) =3477600a(7) =257826240a(8) =22438563840

External references