Just wondering whether anyone knew of any competitions that would serve as a good extracurricular for maths, but are free and don't need a school? I can't find any that can just be done from home - not sure if this is because of cheating or something, probably - as all require a school to sign you up. That's a bit tricky for me.
If not, does anyone have any recommendations for extracurriculars for maths, excluding of course books and MOOCs?