Composite numbers whose prime factors contain no digits other than 5 and 7.

Terms

a(0) =25a(1) =35a(2) =49a(3) =125a(4) =175a(5) =245a(6) =343a(7) =625a(8) =875a(9) =1225a(10) =1715a(11) =2401a(12) =2785a(13) =2885a(14) =3125a(15) =3785a(16) =3899a(17) =4039a(18) =4375a(19) =5299a(20) =6125a(21) =8575a(22) =12005a(23) =13925a(24) =14425a(25) =15625a(26) =16807a(27) =18925a(28) =19495a(29) =20195