a(n) = n*(19*n - 1)/2.

Terms

a(0) =0a(1) =9a(2) =37a(3) =84a(4) =150a(5) =235a(6) =339a(7) =462a(8) =604a(9) =765a(10) =945a(11) =1144a(12) =1362a(13) =1599a(14) =1855a(15) =2130a(16) =2424a(17) =2737a(18) =3069a(19) =3420a(20) =3790a(21) =4179a(22) =4587a(23) =5014a(24) =5460a(25) =5925a(26) =6409a(27) =6912a(28) =7434a(29) =7975