a(n) = 5*Fibonacci(n) + (-1)^n.

Terms

a(0) =1a(1) =4a(2) =6a(3) =9a(4) =16a(5) =24a(6) =41a(7) =64a(8) =106a(9) =169a(10) =276a(11) =444a(12) =721a(13) =1164a(14) =1886a(15) =3049a(16) =4936a(17) =7984a(18) =12921a(19) =20904a(20) =33826a(21) =54729a(22) =88556a(23) =143284a(24) =231841a(25) =375124a(26) =606966a(27) =982089a(28) =1589056a(29) =2571144