Add 1, multiply by 1, add 2, multiply by 2, etc., start with 1.

Terms

a(0) =1a(1) =2a(2) =2a(3) =4a(4) =8a(5) =11a(6) =33a(7) =37a(8) =148a(9) =153a(10) =765a(11) =771a(12) =4626a(13) =4633a(14) =32431a(15) =32439a(16) =259512a(17) =259521a(18) =2335689a(19) =2335699a(20) =23356990a(21) =23357001a(22) =256927011a(23) =256927023a(24) =3083124276a(25) =3083124289a(26) =40080615757a(27) =40080615771a(28) =561128620794a(29) =561128620809