J. Integer Seq. 18(2), Article 15.2.3, 7 p., electronic only (2015)
Summary
Summary: We say that a positive integer $d$ is special if for every integer $m$ there exist nonzero integers $a, b, c$ such that $m = a^{2} + b^{2} - dc^{2}$. In this note we present examples and some properties of special numbers. Moreover, we present an infinite sequence of special numbers.
