Composite numbers whose prime factors contain no digits other than 1 and 9.

Terms

a(0) =121a(1) =209a(2) =361a(3) =1331a(4) =2101a(5) =2189a(6) =2299a(7) =3629a(8) =3781a(9) =3971a(10) =6859a(11) =10021a(12) =10109a(13) =10901a(14) =14641a(15) =17309a(16) =17461a(17) =18829a(18) =21989a(19) =23111a(20) =24079a(21) =25289a(22) =36481a(23) =37981a(24) =38009a(25) =39601a(26) =39919a(27) =41591a(28) =43681a(29) =68951