a(n) = 2^n - A081374(n).

Terms

a(0) =1a(1) =2a(2) =6a(3) =11a(4) =22a(5) =42a(6) =85a(7) =170a(8) =342a(9) =683a(10) =1366a(11) =2730a(12) =5461a(13) =10922a(14) =21846a(15) =43691a(16) =87382a(17) =174762a(18) =349525a(19) =699050a(20) =1398102a(21) =2796203a(22) =5592406a(23) =11184810a(24) =22369621a(25) =44739242a(26) =89478486a(27) =178956971a(28) =357913942a(29) =715827882