a(n) = n*(n^2 + 2*n - 1)/2.

Terms

a(0) =1a(1) =7a(2) =21a(3) =46a(4) =85a(5) =141a(6) =217a(7) =316a(8) =441a(9) =595a(10) =781a(11) =1002a(12) =1261a(13) =1561a(14) =1905a(15) =2296a(16) =2737a(17) =3231a(18) =3781a(19) =4390a(20) =5061a(21) =5797a(22) =6601a(23) =7476a(24) =8425a(25) =9451a(26) =10557a(27) =11746a(28) =13021a(29) =14385