Composite numbers whose prime factors contain no digits other than 1 and 5.

Terms

a(0) =25a(1) =55a(2) =121a(3) =125a(4) =275a(5) =605a(6) =625a(7) =755a(8) =1331a(9) =1375a(10) =1661a(11) =3025a(12) =3125a(13) =3775a(14) =5755a(15) =6655a(16) =6875a(17) =7555a(18) =8305a(19) =12661a(20) =14641a(21) =15125a(22) =15625a(23) =16621a(24) =18271a(25) =18875a(26) =22801a(27) =28775a(28) =33275a(29) =34375