a(n) = (3*n+4)*2^(n-3)-(2*n-1).

Terms

a(0) =2a(1) =8a(2) =25a(3) =67a(4) =165a(5) =387a(6) =881a(7) =1967a(8) =4333a(9) =9451a(10) =20457a(11) =44007a(12) =94181a(13) =200675a(14) =425953a(15) =901087a(16) =1900509a(17) =3997659a(18) =8388569a(19) =17563607a(20) =36700117a(21) =76546003a(22) =159383505a(23) =331349967a(24) =687865805a(25) =1426063307a(26) =2952789961a(27) =6106906567a(28) =12616466373a(29) =26038239171