Right-angled triangles with almost prime hypotenuse

Abstract

The sequence OEIS A281505 consists of distinct odd legs in right triangles with integer sides and prime hypotenuse. In this paper, we count the closely related quantity of even legs with almost prime hypotenuse. More precisely, we obtain the correct order of magnitude upper and lower bounds for the set of distinct even legs with 5-almost prime hypotenuse. This is a strong version of the appropriate analogy to a conjecture of Chow and Pomerance (stated there for prime hypotenuse).