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

Terms

a(0) =1a(1) =3a(2) =11a(3) =43a(4) =167a(5) =631a(6) =2315a(7) =8275a(8) =28943a(9) =99439a(10) =336659a(11) =1126027a(12) =3728279a(13) =12239527a(14) =39890843a(15) =129205699a(16) =416249375a(17) =1334710495a(18) =4262149667a(19) =13560765691a(20) =43005771431a(21) =135988785943a(22) =428882869931