Almost Universal Ternary Sums of Squares and Triangular Numbers

Abstract

For any integer x, let T x denote the triangular number \(\frac{x(x+1)} {2}\). In this paper we give a complete characterization of all the triples of positive integers (α, β, γ) for which the ternary sums \(\alpha {x}^{2} +\beta T_{y} +\gamma T_{z}\) represent all but finitely many positive integers. This resolves a conjecture of Kane and Sun (Trans Am Math Soc 362:6425–6455, 2010, Conjecture 1.19(i)) and complete the characterization of all almost universal ternary mixed sums of squares and triangular numbers.