This paper establishes that for k ≥ 4, all sufficiently large even integers n ≤ N, with at most O(N1/2 − ϑ(k) + ε) exceptions, admit representations as the sum of one square of a prime, four cubes of primes and one kth power of a prime, where the exponent ϑ(k) relies on k. This result sharpens the bound previously obtained by J. J. Li, F. Xue and M. Zhang, Bull. Aust. Math. Soc. 107 (2023) 416–431.
Yuhui Liu (Fri,) studied this question.