What is both even and odd?

Question

Start with any number less than 20. If the number is even, halve it. If the number is odd, add one. Continue using the same rules writing each number one after the other. e.g. 17, 18, 9, 10, 5, 6, 3, 4, 2, 1.

Do they always end in 1? What is the longest list of numbers?

Answer 1

Any number which is a sum of odd number and a even number is both odd and even

eg: 1 = 2 = 3

here 1 is odd and 2 is even. So, 3 is both odd and even