A Horadam-Jacobsthal sequence.

Terms

a(0) =0a(1) =1a(2) =6a(3) =13a(4) =30a(5) =61a(6) =126a(7) =253a(8) =510a(9) =1021a(10) =2046a(11) =4093a(12) =8190a(13) =16381a(14) =32766a(15) =65533a(16) =131070a(17) =262141a(18) =524286a(19) =1048573a(20) =2097150a(21) =4194301a(22) =8388606a(23) =16777213a(24) =33554430a(25) =67108861a(26) =134217726a(27) =268435453a(28) =536870910a(29) =1073741821