Number of trees by stability index.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =1a(6) =1a(7) =2a(8) =4a(9) =8a(10) =16a(11) =34a(12) =72a(13) =158a(14) =348a(15) =784a(16) =1777a(17) =4080a(18) =9425a(19) =21965a(20) =51456a(21) =121300a(22) =287215a(23) =683268a(24) =1631532a(25) =3910235a(26) =9401000a(27) =22670058a(28) =54813780a(29) =132867903