Smallest k for which k, 2k, ... nk all contain the digit 5.

Terms

a(0) =5a(1) =25a(2) =25a(3) =125a(4) =125a(5) =125a(6) =125a(7) =625a(8) =625a(9) =625a(10) =625a(11) =625a(12) =625a(13) =625a(14) =625a(15) =3125a(16) =3125a(17) =3125a(18) =3125a(19) =3125a(20) =3125a(21) =3125a(22) =3125a(23) =3125a(24) =3125a(25) =3125a(26) =3125a(27) =3125a(28) =3125a(29) =3125