I used U+0305 COMBINING OVERLINE to get the line above the digits. I don’t use it at all often, so I had to look it up (I know its name but not its number) and typed it out with my Compose key (using WinCompose since I’m on Windows): `Compose u 3 0 5 Enter`. Since I do do this just occasionally, I’ve just set up `Compose ^ _` for it, by placing this line in my ~/.XCompose:
<Multi_key> <asciicircum> <underscore> : "̅" U0305 # COMBINING OVERLINE
The digits in multiples of sevenths are always the same six digits in order, recurring: 1, 4, 2, 8, 5, 7; it’s just a question of which digit you start from. For one seventh, start with the one (0.14285714285714…); for two, the two (0.285714285714…); three, the four (0.428571428…); four, the five; five, the seven; six, the eight.