Number of isomers of alkyl homologs of adamantane with n carbon atoms.

Terms

a(0) =1a(1) =2a(2) =11a(3) =49a(4) =217a(5) =858a(6) =3314a(7) =11995a(8) =41921a(9) =141163a(10) =462674a(11) =1480017a(12) =4644331a(13) =14332801a(14) =43628996a(15) =131248423a(16) =390921934a(17) =1154427742a(18) =3384244322a(19) =9858374939a(20) =28560865688a(21) =82351168539a(22) =236465407302a(23) =676536049902