Number of ethylene derivatives with n carbon atoms.

Terms

a(0) =1a(1) =1a(2) =3a(3) =5a(4) =13a(5) =27a(6) =66a(7) =153a(8) =377a(9) =914a(10) =2281a(11) =5690a(12) =14397a(13) =36564a(14) =93650a(15) =240916a(16) =623338a(17) =1619346a(18) =4224993a(19) =11062046a(20) =29062341a(21) =76581151a(22) =202365823a(23) =536113477a(24) =1423665699a(25) =3788843391a(26) =10103901486a(27) =26995498151a(28) =72253682560a(29) =193706542776