Number of achiral free pure multifunctions with n unlabeled leaves.

Terms

a(0) =1a(1) =1a(2) =3a(3) =9a(4) =30a(5) =102a(6) =369a(7) =1362a(8) =5181a(9) =20064a(10) =79035a(11) =315366a(12) =1272789a(13) =5185080a(14) =21296196a(15) =88083993a(16) =366584253a(17) =1533953100a(18) =6449904138a(19) =27238006971a(20) =115475933202a(21) =491293053093