a(n) = Fibonacci(n)*Fibonacci(3n)/2.

Terms

a(0) =0a(1) =1a(2) =4a(3) =34a(4) =216a(5) =1525a(6) =10336a(7) =71149a(8) =486864a(9) =3339106a(10) =22881100a(11) =156843721a(12) =1074985344a(13) =7368157369a(14) =50501844796a(15) =346145466850