 evil |
 odious |
| The first 16 evil and odious numbers in little-endian binary. It can be seen, that both sequences differ only in the least significant bits, which form the Thue–Morse sequence for the evil, and its negation for the odious numbers. The other bits form the even numbers. | |
In number theory, an odious number is a positive integer that has an odd number of 1s in its binary expansion. Non-negative integers that are not odious are called evil numbers.
In computer science, an odious number is said to have odd parity.