Number of oriented trees rooted at an arc.

Terms

a(0) =1a(1) =4a(2) =18a(3) =80a(4) =367a(5) =1708a(6) =8122a(7) =39204a(8) =191963a(9) =950984a(10) =4759626a(11) =24030736a(12) =122258314a(13) =626162464a(14) =3225926450a(15) =16706775984a(16) =86928097451a(17) =454203897192