Basically if you spot the sequence posted by the previous guy, post the next few items in it and assuming it's correct start a new sequence(or say you don't want to and let someone else do it).
For instance:
THERE's NO WAY YOU'LL SPOT THIS SEQUENCE ... LULZ : 1,3,5,7,9
It was an uphill battle but i finally figured it out, i believe the next items would be: 11,13,15
Also, you don't have to do only numerical sequences, so you could have for instance
Would be a sequence of danish prime ministers starting from 1918.Carl Theodor Zahle, Otto Liebe, Michael Pedersen Friis, Niels Neergaard
Just make sure that you post enough elements of the sequence for it to be discernible from random shit, and if no one's coming close to guessing, it might be nice to give hints/the solution.
When answering to a sequence post enough terms to show you really got it.
Let's see if this works:
1,4,1,5,9,2,6,5 ...