3^n-Jacobsthal(n).

Terms

a(0) =1a(1) =2a(2) =8a(3) =24a(4) =76a(5) =232a(6) =708a(7) =2144a(8) =6476a(9) =19512a(10) =58708a(11) =176464a(12) =530076a(13) =1591592a(14) =4777508a(15) =14337984a(16) =43024876a(17) =129096472a(18) =387333108a(19) =1162086704a(20) =3486434876a(21) =10459654152a(22) =31379661508a(23) =94140382624a(24) =282423944076a(25) =847277424632