a(n) = n*(21*n-17)/2.

Terms

a(0) =0a(1) =2a(2) =25a(3) =69a(4) =134a(5) =220a(6) =327a(7) =455a(8) =604a(9) =774a(10) =965a(11) =1177a(12) =1410a(13) =1664a(14) =1939a(15) =2235a(16) =2552a(17) =2890a(18) =3249a(19) =3629a(20) =4030a(21) =4452a(22) =4895a(23) =5359a(24) =5844a(25) =6350a(26) =6877a(27) =7425a(28) =7994a(29) =8584