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

Terms

a(0) =0a(1) =0a(2) =5a(3) =11a(4) =23a(5) =42a(6) =74a(7) =126a(8) =211a(9) =349a(10) =573a(11) =936a(12) =1524a(13) =2476a(14) =4017a(15) =6511a(16) =10547a(17) =17078a(18) =27646a(19) =44746a(20) =72415a(21) =117185a(22) =189625a(23) =306836a(24) =496488a(25) =803352a(26) =1299869a(27) =2103251a(28) =3403151a(29) =5506434