a(n) = Lucas(n+4) - (3*n+7).

Terms

a(0) =1a(1) =5a(2) =13a(3) =28a(4) =54a(5) =98a(6) =171a(7) =291a(8) =487a(9) =806a(10) =1324a(11) =2164a(12) =3525a(13) =5729a(14) =9297a(15) =15072a(16) =24418a(17) =39542a(18) =64015a(19) =103615a(20) =167691a(21) =271370a(22) =439128a(23) =710568a(24) =1149769a(25) =1860413a(26) =3010261a(27) =4870756a(28) =7881102a(29) =12751946