Even and Odd Numbers Song for Kids | Odds and Evens for Grades 2 & 3
https://www.youtube.com/watch?v=-kHtGbnYKGc
The fact that zero is even, together with the fact that even and odd numbers alternate, is enough to determine the parity of every other natural number. This idea can be formalized into a recursive definition of the set of even natural numbers: 0 is even.