a(n) = n*(n + 1)*(19*n - 16)/6.

Terms

a(0) =0a(1) =1a(2) =22a(3) =82a(4) =200a(5) =395a(6) =686a(7) =1092a(8) =1632a(9) =2325a(10) =3190a(11) =4246a(12) =5512a(13) =7007a(14) =8750a(15) =10760a(16) =13056a(17) =15657a(18) =18582a(19) =21850a(20) =25480a(21) =29491a(22) =33902a(23) =38732a(24) =44000a(25) =49725a(26) =55926a(27) =62622a(28) =69832a(29) =77575