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

Terms

a(0) =1a(1) =5a(2) =22a(3) =89a(4) =340a(5) =1247a(6) =4438a(7) =15437a(8) =52744a(9) =177659a(10) =591514a(11) =1950665a(12) =6381388a(13) =20734391a(14) =66977950a(15) =215266373a(16) =688813072a(17) =2195513843a(18) =6973830946a(19) =22083492161a(20) =69736736596a(21) =219669514415a(22) =690387505702