Generalized Jacobsthal numbers.

Terms

a(0) =0a(1) =1a(2) =1a(3) =4a(4) =8a(5) =19a(6) =39a(7) =82a(8) =166a(9) =337a(10) =677a(11) =1360a(12) =2724a(13) =5455a(14) =10915a(15) =21838a(16) =43682a(17) =87373a(18) =174753a(19) =349516a(20) =699040a(21) =1398091a(22) =2796191a(23) =5592394a(24) =11184798a(25) =22369609a(26) =44739229a(27) =89478472a(28) =178956956a(29) =357913927