a(n) = (A212146(n)-1)/2.

Terms

a(0) =0a(1) =1a(2) =3a(3) =6a(4) =11a(5) =18a(6) =29a(7) =45a(8) =70a(9) =108a(10) =170a(11) =270a(12) =439a(13) =726a(14) =1227a(15) =2108a(16) =3685a(17) =6523a(18) =11687a(19) =21129a(20) =38513a(21) =70649a(22) =130347a(23) =241610a(24) =449735a(25) =840134a(26) =1574537a(27) =2959350a(28) =5576730a(29) =10533846