Number of "funny trees" on n nodes.

Terms

a(0) =0a(1) =2a(2) =3a(3) =9a(4) =30a(5) =110a(6) =423a(7) =1706a(8) =7085a(9) =30186a(10) =131071a(11) =578194a(12) =2583377a(13) =11667874a(14) =53180604a(15) =244301512a(16) =1129947243a(17) =5257592237a(18) =24592945975a(19) =115578827200a(20) =545478791124