Numbers of the form 3^i*11^j.

Terms

a(0) =1a(1) =3a(2) =9a(3) =11a(4) =27a(5) =33a(6) =81a(7) =99a(8) =121a(9) =243a(10) =297a(11) =363a(12) =729a(13) =891a(14) =1089a(15) =1331a(16) =2187a(17) =2673a(18) =3267a(19) =3993a(20) =6561a(21) =8019a(22) =9801a(23) =11979a(24) =14641a(25) =19683a(26) =24057a(27) =29403a(28) =35937a(29) =43923