A Circle Method Approach to K-Multimagic Squares
In this paper we investigate K-multimagic squares of order N, these are N×N magic squares which remain magic after raising each element to the kth power for all 2≤k≤K. Given K≥2, we consider the problem of establishing the smallest integer N(K) for which there exists non-trivial K-multimagic squares of order N(K). Previous results on multimagic squares show that N(K)≤(4K−2)K for large K. Here we utilize the Hardy-Littlewood circle method and establish the bound
N(K)≤2K(K+1)+1.
Via an argument of Granville's we additionally deduce the existence of infinitely many non-trivial prime valued K-multimagic squares of order 2K(K+1)+1.