a(n)=(n^5-n-30)/30.

Terms

a(0) =-1a(1) =-1a(2) =0a(3) =7a(4) =33a(5) =103a(6) =258a(7) =559a(8) =1091a(9) =1967a(10) =3332a(11) =5367a(12) =8293a(13) =12375a(14) =17926a(15) =25311a(16) =34951a(17) =47327a(18) =62984a(19) =82535a(20) =106665a(21) =136135a(22) =171786a(23) =214543a(24) =265419a(25) =325519a(26) =396044a(27) =478295a(28) =573677a(29) =683703