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

Terms

a(0) =2a(1) =7a(2) =20a(3) =52a(4) =128a(5) =304a(6) =704a(7) =1600a(8) =3584a(9) =7936a(10) =17408a(11) =37888a(12) =81920a(13) =176128a(14) =376832a(15) =802816a(16) =1703936a(17) =3604480a(18) =7602176a(19) =15990784a(20) =33554432a(21) =70254592a(22) =146800640a(23) =306184192a(24) =637534208a(25) =1325400064a(26) =2751463424a(27) =5704253440a(28) =11811160064a(29) =24427626496