a(n) = 225*(n-1)*(n-2)/2.

Terms

a(0) =225a(1) =675a(2) =1350a(3) =2250a(4) =3375a(5) =4725a(6) =6300a(7) =8100a(8) =10125a(9) =12375a(10) =14850a(11) =17550a(12) =20475a(13) =23625a(14) =27000a(15) =30600a(16) =34425a(17) =38475a(18) =42750a(19) =47250a(20) =51975a(21) =56925a(22) =62100a(23) =67500a(24) =73125a(25) =78975a(26) =85050a(27) =91350a(28) =97875a(29) =104625