that's how you count in base 2 :P :
10001 10010 10011 10100 10101 10110 10111 11000 11001 11010 11011 11100 11101 11110 11111 ? see the pattern
or easier just convert to decimal => decimal to bin
1 * 2^4 + 0 * 2^3 + 0 *2^2 +0 * 2^1 + 0 * 2^0 = 16
after 16 is 17 wow
so
17/2 => (17 can't be divided over 2 without a reminder (8.5) or 1 is reminder)
8 (1) reminder
4 (0) reminder
2 (0) reminder
1 (0) reminder
0 (1) reminder (1 /2 = 0.5 not a whole number always ends like that)
collect all reminders:
10001