Number of unlabeled 2-ary cacti having n polygons. Also number of bicolored plane trees with n edges.

A054357

Number of unlabeled 2-ary cacti having n polygons. Also number of bicolored plane trees with n edges.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =3a(4) =6a(5) =10a(6) =28a(7) =63a(8) =190a(9) =546a(10) =1708a(11) =5346a(12) =17428a(13) =57148a(14) =191280a(15) =646363a(16) =2210670a(17) =7626166a(18) =26538292a(19) =93013854a(20) =328215300a(21) =1165060668a(22) =4158330416a(23) =14915635378a(24) =53746119972a(25) =194477856100a(26) =706437056648

External references