I am a huge fan of number scrolls.
They are just a strip of paper that start at any number (depending on ability) and can be used to add 1, add 2, skip count, double, add or subtract from.
What I love about them is that kids love them and they are learning at the same time.
This little group were being independent and were using the constant function on the calculator to check each response as they were recorded. This ensures a self checking component and you don't just have a random string of numbers.
They can be done individually or in pairs or in a group of three.
If the paper was bigger - the group can be bigger.
This group were setting their own goals and some were skip counting by 6, 8 or 11 from a non zero start.