ThmDex – An index of mathematical definitions, results, and conjectures.
C4: Goldbach conjecture
C19: Legendre's conjecture
C9: Vizing's conjecture
C5: Twin prime conjecture
C2: Riemann hypothesis
C17: Andrica's conjecture
C3: Collatz conjecture
C14: Sendov's conjecture
C7: Euclid number conjecture
C15: Singmaster's conjecture