a(n) = 7*a(n-2), a(0) = 1, a(1) = 2.

Terms

a(0) =1a(1) =2a(2) =7a(3) =14a(4) =49a(5) =98a(6) =343a(7) =686a(8) =2401a(9) =4802a(10) =16807a(11) =33614a(12) =117649a(13) =235298a(14) =823543a(15) =1647086a(16) =5764801a(17) =11529602a(18) =40353607a(19) =80707214a(20) =282475249a(21) =564950498a(22) =1977326743a(23) =3954653486a(24) =13841287201a(25) =27682574402a(26) =96889010407a(27) =193778020814