>>> for x in ['{0:3n} 0b{0:08b} {1}'.format(x, ('X' if (x & 0b00001000) and (x & 0b00000100) else '')) for x in range(0,40)]: print(x)
...
  0 0b00000000
  1 0b00000001
  2 0b00000010
  3 0b00000011
  4 0b00000100
  5 0b00000101
  6 0b00000110
  7 0b00000111
  8 0b00001000
  9 0b00001001
 10 0b00001010
 11 0b00001011
 12 0b00001100 X
 13 0b00001101 X
 14 0b00001110 X
 15 0b00001111 X
 16 0b00010000
 17 0b00010001
 18 0b00010010
 19 0b00010011
 20 0b00010100
 21 0b00010101
 22 0b00010110
 23 0b00010111
 24 0b00011000
 25 0b00011001
 26 0b00011010
 27 0b00011011
 28 0b00011100 X
 29 0b00011101 X
 30 0b00011110 X
 31 0b00011111 X
 32 0b00100000
 33 0b00100001
 34 0b00100010
 35 0b00100011
 36 0b00100100
 37 0b00100101
 38 0b00100110
 39 0b00100111