2*Jacobsthal(n-1)*Fibonacci(n).

Terms

a(0) =0a(1) =0a(2) =2a(3) =4a(4) =18a(5) =50a(6) =176a(7) =546a(8) =1806a(9) =5780a(10) =18810a(11) =60698a(12) =196704a(13) =636090a(14) =2059174a(15) =6662420a(16) =21562002a(17) =69772930a(18) =225795088a(19) =730679922a(20) =2364543390a(21) =7651801300a(22) =24761784522a(23) =80130760714a(24) =259308681408a(25) =839140370250