a(n) = 164*2^n - 99.

Terms

a(0) =65a(1) =229a(2) =557a(3) =1213a(4) =2525a(5) =5149a(6) =10397a(7) =20893a(8) =41885a(9) =83869a(10) =167837a(11) =335773a(12) =671645a(13) =1343389a(14) =2686877a(15) =5373853a(16) =10747805a(17) =21495709a(18) =42991517a(19) =85983133a(20) =171966365a(21) =343932829a(22) =687865757a(23) =1375731613a(24) =2751463325a(25) =5502926749a(26) =11005853597a(27) =22011707293a(28) =44023414685a(29) =88046829469