a(n) = n*(21*n + 1)/2.

Terms

a(0) =0a(1) =11a(2) =43a(3) =96a(4) =170a(5) =265a(6) =381a(7) =518a(8) =676a(9) =855a(10) =1055a(11) =1276a(12) =1518a(13) =1781a(14) =2065a(15) =2370a(16) =2696a(17) =3043a(18) =3411a(19) =3800a(20) =4210a(21) =4641a(22) =5093a(23) =5566a(24) =6060a(25) =6575a(26) =7111a(27) =7668a(28) =8246a(29) =8845