Two problems from the world's happiest country.
13:09
two nice superfactorial problems
9:33
this sum may stump you
26:08
there are only two prime matrices.
17:34
A minimum problem that is too much for calculus to handle.
45:23
Some 122 Questions
9:32
A nice problem from the 2012 math olympiad
41:44
Numberphile v. Math: the truth about 1+2+3+...=-1/12
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