Sum_{i=0..3} binomial(Fibonacci(n),i).

Terms

a(0) =1a(1) =2a(2) =2a(3) =4a(4) =8a(5) =26a(6) =93a(7) =378a(8) =1562a(9) =6580a(10) =27776a(11) =117570a(12) =497785a(13) =2108418a(14) =8930754a(15) =37830676a(16) =160251624a(17) =678835194a(18) =2875587605a(19) =12181180442a(20) =51600296826a(21) =218582354212a(22) =925929680832