Singly and doubly even

"Singly even" and "doubly even" typically refer to types of numbers in the context of mathematics, particularly in discussing properties of integers or sets of integers. 1. **Singly Even Numbers**: A number is termed "singly even" if it is divisible by 2 but not by 4. In other words, singly even numbers can be expressed in the form \(4k + 2\), where \(k\) is an integer.