a(n) = 1 + 2^(n-1) + n for n > 0, a(0) = 2.

Terms

a(0) =2a(1) =3a(2) =5a(3) =8a(4) =13a(5) =22a(6) =39a(7) =72a(8) =137a(9) =266a(10) =523a(11) =1036a(12) =2061a(13) =4110a(14) =8207a(15) =16400a(16) =32785a(17) =65554a(18) =131091a(19) =262164a(20) =524309a(21) =1048598a(22) =2097175a(23) =4194328a(24) =8388633a(25) =16777242a(26) =33554459a(27) =67108892a(28) =134217757a(29) =268435486