a(n) = n*L(n) + (n-1)*L(n-1) where L(n) is the Lucas number.

Terms

a(0) =7a(1) =18a(2) =40a(3) =83a(4) =163a(5) =311a(6) =579a(7) =1060a(8) =1914a(9) =3419a(10) =6053a(11) =10637a(12) =18575a(13) =32262a(14) =55772a(15) =96019a(16) =164711a(17) =281635a(18) =480171a(19) =816536a(20) =1385262a(21) =2345083a(22) =3962185a(23) =6682393a(24) =11251543a(25) =18916026a(26) =31756624a(27) =53243795a(28) =89160619a(29) =149135759