a(n) = a(n-1) + a(n-2) + n + 3 with n>1, a(0)=1, a(1)=2.

Terms

a(0) =1a(1) =2a(2) =8a(3) =16a(4) =31a(5) =55a(6) =95a(7) =160a(8) =266a(9) =438a(10) =717a(11) =1169a(12) =1901a(13) =3086a(14) =5004a(15) =8108a(16) =13131a(17) =21259a(18) =34411a(19) =55692a(20) =90126a(21) =145842a(22) =235993a(23) =381861a(24) =617881a(25) =999770a(26) =1617680a(27) =2617480a(28) =4235191a(29) =6852703