a(n) = 10*3^n+1.

Terms

a(0) =11a(1) =31a(2) =91a(3) =271a(4) =811a(5) =2431a(6) =7291a(7) =21871a(8) =65611a(9) =196831a(10) =590491a(11) =1771471a(12) =5314411a(13) =15943231a(14) =47829691a(15) =143489071a(16) =430467211a(17) =1291401631a(18) =3874204891a(19) =11622614671a(20) =34867844011a(21) =104603532031a(22) =313810596091a(23) =941431788271