a(n) = A178901(n)/n.

Terms

a(0) =2a(1) =2a(2) =2a(3) =3a(4) =4a(5) =6a(6) =10a(7) =17a(8) =30a(9) =54a(10) =98a(11) =179a(12) =330a(13) =612a(14) =1142a(15) =2141a(16) =4030a(17) =7612a(18) =14422a(19) =27401a(20) =52192a(21) =99639a(22) =190613a(23) =365341a(24) =701454a(25) =1348950a(26) =2597977a(27) =5010384a(28) =9675224a(29) =18705433