In number theory, an evil number is a non-negative number that has an even number of 1s in its binary expansion.
The first evil numbers are:
0, 3, 5, 6, 9, 10, 12, 15, 17, 18, 20, 23, 24, 27, 29, 30, 33, 34, 36, 39 ...These numbers give the positions of the zero values in the Thue–Morse sequence.
Numbers that are not evil are called odious numbers.
References
Evil number Wikipedia(Text) CC BY-SA