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

Terms

a(0) =1a(1) =1a(2) =5a(3) =10a(4) =20a(5) =36a(6) =63a(7) =107a(8) =179a(9) =296a(10) =486a(11) =794a(12) =1293a(13) =2101a(14) =3409a(15) =5526a(16) =8952a(17) =14496a(18) =23467a(19) =37983a(20) =61471a(21) =99476a(22) =160970a(23) =260470a(24) =421465a(25) =681961a(26) =1103453a(27) =1785442a(28) =2888924a(29) =4674396