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

Terms

a(0) =0a(1) =0a(2) =4a(3) =9a(4) =19a(5) =35a(6) =62a(7) =106a(8) =178a(9) =295a(10) =485a(11) =793a(12) =1292a(13) =2100a(14) =3408a(15) =5525a(16) =8951a(17) =14495a(18) =23466a(19) =37982a(20) =61470a(21) =99475a(22) =160969a(23) =260469a(24) =421464a(25) =681960a(26) =1103452a(27) =1785441a(28) =2888923a(29) =4674395