a(n) = 68*2^n + 358.

Terms

a(0) =426a(1) =494a(2) =630a(3) =902a(4) =1446a(5) =2534a(6) =4710a(7) =9062a(8) =17766a(9) =35174a(10) =69990a(11) =139622a(12) =278886a(13) =557414a(14) =1114470a(15) =2228582a(16) =4456806a(17) =8913254a(18) =17826150a(19) =35651942a(20) =71303526a(21) =142606694a(22) =285213030a(23) =570425702a(24) =1140851046a(25) =2281701734a(26) =4563403110a(27) =9126805862a(28) =18253611366a(29) =36507222374