a(n) = n * Fibonacci(n+1).

Terms

a(0) =0a(1) =1a(2) =4a(3) =9a(4) =20a(5) =40a(6) =78a(7) =147a(8) =272a(9) =495a(10) =890a(11) =1584a(12) =2796a(13) =4901a(14) =8540a(15) =14805a(16) =25552a(17) =43928a(18) =75258a(19) =128535a(20) =218920a(21) =371931a(22) =630454a(23) =1066464a(24) =1800600a(25) =3034825a(26) =5106868a(27) =8580897a(28) =14398412a(29) =24129160