Number of 2-trees rooted at an asymmetric edge.

Terms

a(0) =0a(1) =1a(2) =4a(3) =18a(4) =77a(5) =346a(6) =1578a(7) =7396a(8) =35297a(9) =171352a(10) =843067a(11) =4196502a(12) =21092793a(13) =106912874a(14) =545851964a(15) =2804641873a(16) =14491337393a(17) =75248330560a(18) =392476202012