Jacobsthal numbers(A001045) + 1.

Terms

a(0) =1a(1) =2a(2) =2a(3) =4a(4) =6a(5) =12a(6) =22a(7) =44a(8) =86a(9) =172a(10) =342a(11) =684a(12) =1366a(13) =2732a(14) =5462a(15) =10924a(16) =21846a(17) =43692a(18) =87382a(19) =174764a(20) =349526a(21) =699052a(22) =1398102a(23) =2796204a(24) =5592406a(25) =11184812a(26) =22369622a(27) =44739244a(28) =89478486a(29) =178956972