a(n) = 680*2^n - 548.

Terms

a(0) =132a(1) =812a(2) =2172a(3) =4892a(4) =10332a(5) =21212a(6) =42972a(7) =86492a(8) =173532a(9) =347612a(10) =695772a(11) =1392092a(12) =2784732a(13) =5570012a(14) =11140572a(15) =22281692a(16) =44563932a(17) =89128412a(18) =178257372a(19) =356515292a(20) =713031132a(21) =1426062812a(22) =2852126172a(23) =5704252892a(24) =11408506332a(25) =22817013212a(26) =45634026972a(27) =91268054492a(28) =182536109532a(29) =365072219612