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arXiv · 0804.3750

Mixed sums of squares and triangular numbers (III)

Byeong-Kweon Oh·Zhi-Wei Sun
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Abstract

In this paper we confirm a conjecture of Sun which states that each positive integer is a sum of a square, an odd square and a triangular number. Given any positive integer m, we show that p=2m+1 is a prime congruent to 3 modulo 4 if and only if T_m=m(m+1)/2 cannot be expressed as a sum of two odd squares and a triangular number, i.e., p^2=x^2+8(y^2+z^2) for no odd integers x,y,z. We also show that a positive integer cannot be written as a sum of an odd square and two triangular numbers if and only if it is of the form 2T_m (m>0) with 2m+1 having no prime divisor congruent to 3 modulo 4.

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Byeong-Kweon Oh, Zhi-Wei Sun. 2009-02-07. Mixed sums of squares and triangular numbers (III). https://arxiv.org/abs/0804.3750

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