3*Fibonacci(n) - 11.

Terms

a(0) =4a(1) =13a(2) =28a(3) =52a(4) =91a(5) =154a(6) =256a(7) =421a(8) =688a(9) =1120a(10) =1819a(11) =2950a(12) =4780a(13) =7741a(14) =12532a(15) =20284a(16) =32827a(17) =53122a(18) =85960a(19) =139093a(20) =225064a(21) =364168a(22) =589243a(23) =953422a(24) =1542676a(25) =2496109a(26) =4038796a(27) =6534916a(28) =10573723a(29) =17108650