Actually, there were never more than 6 of them and that wasn't until episode 4 and for the last two series there were only 5 and Blake wasn't in it. Talk about false advertising.

So join our campaign to rename the show "Blake's or Whoever's 7 (Actually 6) or Lower" or we'll tranquillise you, brainwash you, frame you for an unspeakable crime and fire you off into deep space.