Euler’s conjecture was a generalization of Fermat’s Last Theorem that has since been proved untrue. It stated that n−1 nth powers could never add to an nth power. For n = 3 this is a special case of Fermat and so true. But a counterexample to n = 5 was found in 1966 and the smallest counterexample to n = 4 is now known to be ${95800}^4+{217519}^4+{414560}^4={422481}^4.$