a(n) = 282*2^n - 150.

Terms

a(0) =132a(1) =414a(2) =978a(3) =2106a(4) =4362a(5) =8874a(6) =17898a(7) =35946a(8) =72042a(9) =144234a(10) =288618a(11) =577386a(12) =1154922a(13) =2309994a(14) =4620138a(15) =9240426a(16) =18481002a(17) =36962154a(18) =73924458a(19) =147849066a(20) =295698282a(21) =591396714a(22) =1182793578a(23) =2365587306a(24) =4731174762a(25) =9462349674a(26) =18924699498a(27) =37849399146a(28) =75698798442a(29) =151397597034