a(n) = 81*n^2 + 9.

Terms

a(0) =90a(1) =333a(2) =738a(3) =1305a(4) =2034a(5) =2925a(6) =3978a(7) =5193a(8) =6570a(9) =8109a(10) =9810a(11) =11673a(12) =13698a(13) =15885a(14) =18234a(15) =20745a(16) =23418a(17) =26253a(18) =29250a(19) =32409a(20) =35730a(21) =39213a(22) =42858a(23) =46665a(24) =50634a(25) =54765a(26) =59058a(27) =63513a(28) =68130a(29) =72909