a(n) = n*(16*n^2 - 21*n + 7)/2.

Terms

a(0) =0a(1) =1a(2) =29a(3) =132a(4) =358a(5) =755a(6) =1371a(7) =2254a(8) =3452a(9) =5013a(10) =6985a(11) =9416a(12) =12354a(13) =15847a(14) =19943a(15) =24690a(16) =30136a(17) =36329a(18) =43317a(19) =51148a(20) =59870a(21) =69531a(22) =80179a(23) =91862a(24) =104628a(25) =118525a(26) =133601a(27) =149904a(28) =167482a(29) =186383