What does EOO mean in homework?

EOO stands for Every Other Odd

For example if problems # 3-23 were assigned; you would do problem 3 and skip number 5, do number 7 and skip 9, do 11 and skip 13, etc. until you reach number 23.  In other words, you would have completed numbers 3, 7, 11, 15, 19, and 23.