a(n) = 3*2^n + 2.

Terms

a(0) =5a(1) =8a(2) =14a(3) =26a(4) =50a(5) =98a(6) =194a(7) =386a(8) =770a(9) =1538a(10) =3074a(11) =6146a(12) =12290a(13) =24578a(14) =49154a(15) =98306a(16) =196610a(17) =393218a(18) =786434a(19) =1572866a(20) =3145730a(21) =6291458a(22) =12582914a(23) =25165826a(24) =50331650a(25) =100663298a(26) =201326594a(27) =402653186a(28) =805306370a(29) =1610612738