a(n) = 2*L(n) + L(n-1) - n, L(n) = n-th Lucas number A000204(n).

Terms

a(0) =1a(1) =5a(2) =8a(3) =14a(4) =24a(5) =41a(6) =69a(7) =115a(8) =190a(9) =312a(10) =510a(11) =831a(12) =1351a(13) =2193a(14) =3556a(15) =5762a(16) =9332a(17) =15109a(18) =24457a(19) =39583a(20) =64058a(21) =103660a(22) =167738a(23) =271419a(24) =439179a(25) =710621a(26) =1149824a(27) =1860470a(28) =3010320a(29) =4870817