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

Terms

a(0) =1a(1) =2a(2) =7a(3) =23a(4) =67a(5) =179a(6) =451a(7) =1091a(8) =2563a(9) =5891a(10) =13315a(11) =29699a(12) =65539a(13) =143363a(14) =311299a(15) =671747a(16) =1441795a(17) =3080195a(18) =6553603a(19) =13893635a(20) =29360131a(21) =61865987a(22) =130023427a(23) =272629763a(24) =570425347a(25) =1191182339a(26) =2483027971a(27) =5167382531a(28) =10737418243a(29) =22280142851