Fermat–Catalan conjecture

there are finitely many distinct solutions (a^m, b^n, c^k) to the equation a^m + b^n = c^k with a, b, c being positive coprime integers and m, n, k being positive integers satisfying 1/m + 1/n + 1/k < 1.

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Source: List of unsolved problems in mathematics (CC BY-SA 4.0)