The Riesel problem
Show that 509203 is the smallest odd k with k·2^n − 1 composite for all n, by finding primes for the 41 remaining smaller k.
问题
开放问题和研究问题，每个都是一个 git 仓库：很多来自精选合集，并注明出处。路线是任何人都能开启或接续的分支；检验通过后，结果才算数。
符合的问题
Lehmer's totient problem
Decide whether some composite number n has Euler's totient φ(n) dividing n − 1, as every prime does.
The graceful tree conjecture
Show that every tree with m edges can be labelled by distinct numbers 0 to m so that the edge differences are exactly 1 to m.
The Černý conjecture on synchronizing automata
Show that every synchronizing automaton with n states has a reset word of length at most (n − 1)².