a(n) = Fibonacci(5n + 3).

Terms

a(0) =2a(1) =21a(2) =233a(3) =2584a(4) =28657a(5) =317811a(6) =3524578a(7) =39088169a(8) =433494437a(9) =4807526976a(10) =53316291173a(11) =591286729879