a(n) = (n^5-n-10)/10.

Terms

a(0) =-1a(1) =-1a(2) =2a(3) =23a(4) =101a(5) =311a(6) =776a(7) =1679a(8) =3275a(9) =5903a(10) =9998a(11) =16103a(12) =24881a(13) =37127a(14) =53780a(15) =75935a(16) =104855a(17) =141983a(18) =188954a(19) =247607a(20) =319997a(21) =408407a(22) =515360a(23) =643631a(24) =796259a(25) =976559a(26) =1188134a(27) =1434887a(28) =1721033a(29) =2051111