Composite numbers that contain only prime digits and whose prime factors contain only prime digits.

Terms

a(0) =25a(1) =27a(2) =32a(3) =35a(4) =72a(5) =75a(6) =222a(7) =225a(8) =252a(9) =322a(10) =333a(11) =375a(12) =525a(13) =552a(14) =555a(15) =575a(16) =735a(17) =777a(18) =2352a(19) =2553a(20) =2555a(21) =2775a(22) =3357a(23) =3375a(24) =3552a(25) =3577a(26) =5222a(27) =5352a(28) =5575a(29) =7252