a(n) = n*Lucas(2*n).

Terms

a(0) =0a(1) =3a(2) =14a(3) =54a(4) =188a(5) =615a(6) =1932a(7) =5901a(8) =17656a(9) =52002a(10) =151270a(11) =435633a(12) =1244184a(13) =3528759a(14) =9949058a(15) =27907470a(16) =77933552a(17) =216784731a(18) =600935076a(19) =1660672257a(20) =4576522540a(21) =12580566138a(22) =34504747354a(23) =94440719589a(24) =257998970928a(25) =703593828075