a(n) = 729*n - 531.

Terms

a(0) =198a(1) =927a(2) =1656a(3) =2385a(4) =3114a(5) =3843a(6) =4572a(7) =5301a(8) =6030a(9) =6759a(10) =7488a(11) =8217a(12) =8946a(13) =9675a(14) =10404a(15) =11133a(16) =11862a(17) =12591a(18) =13320a(19) =14049a(20) =14778a(21) =15507a(22) =16236a(23) =16965a(24) =17694a(25) =18423a(26) =19152a(27) =19881a(28) =20610a(29) =21339