a(n) = Fibonacci(4*n).

Terms

a(0) =0a(1) =3a(2) =21a(3) =144a(4) =987a(5) =6765a(6) =46368a(7) =317811a(8) =2178309a(9) =14930352a(10) =102334155a(11) =701408733a(12) =4807526976a(13) =32951280099a(14) =225851433717