Set Definition by Predicate/Examples/Sums of Two Squares

Examples of Set Definition by Predicate

Let $S$ be the set defined as:

$S := \set {n: n = x^2 + y^2 \text { and } x, y \in \Z}$

The $C$ is the set of all integers which can be written as the sum of two squares.

Sources

• 1964: Steven A. Gaal: Point Set Topology ... (previous) ... (next): Introduction to Set Theory: $1$. Elementary Operations on Sets