a(n) = 729*n - 198.

Terms

a(0) =531a(1) =1260a(2) =1989a(3) =2718a(4) =3447a(5) =4176a(6) =4905a(7) =5634a(8) =6363a(9) =7092a(10) =7821a(11) =8550a(12) =9279a(13) =10008a(14) =10737a(15) =11466a(16) =12195a(17) =12924a(18) =13653a(19) =14382a(20) =15111a(21) =15840a(22) =16569a(23) =17298a(24) =18027a(25) =18756a(26) =19485a(27) =20214a(28) =20943a(29) =21672