a(n) = Fibonacci(n+2)^2 - 1.

Terms

a(0) =0a(1) =3a(2) =8a(3) =24a(4) =63a(5) =168a(6) =440a(7) =1155a(8) =3024a(9) =7920a(10) =20735a(11) =54288a(12) =142128a(13) =372099a(14) =974168a(15) =2550408a(16) =6677055a(17) =17480760a(18) =45765224a(19) =119814915a(20) =313679520a(21) =821223648a(22) =2149991423a(23) =5628750624a(24) =14736260448a(25) =38580030723a(26) =101003831720