Here is a nice simple idea for sequences to get students on their feet from my colleague Chris Hordern.  

He asked groups of year 8 students to decide on a sequence, then come to the front of the class and be a number in that sequence.   The rest of the class had to work out what the sequence was...

How could you develop this further? Could you jumble up the sequences, or maybe someone in the sequence stays silent and you have to guess their number?  Or what if every second person in the sequence calls out their number? How does this new sequence relate to the original one?  

Maybe you could get everyone in the class to stand up in a long row and the first two people start the (arithmetic) sequence; can everyone else in the class work out what number they are? What number is person number 10? What would be person number 100? What if everyone in the year stood in a line?

Perhaps some people in the class might be in two sequences, their own group and another one... what does that tell us?