Jacobsthal numbers A001045, every second term incremented by 1.

Terms

a(0) =0a(1) =2a(2) =1a(3) =4a(4) =5a(5) =12a(6) =21a(7) =44a(8) =85a(9) =172a(10) =341a(11) =684a(12) =1365a(13) =2732a(14) =5461a(15) =10924a(16) =21845a(17) =43692a(18) =87381a(19) =174764a(20) =349525a(21) =699052a(22) =1398101a(23) =2796204a(24) =5592405a(25) =11184812a(26) =22369621a(27) =44739244a(28) =89478485a(29) =178956972