The next number should be 13112221. Why?
Because each of these numbers describes the previous number. Starting with 1, the 2nd line is 11 (one one), then the 3rd line describes 11 as 21(two ones). Then the 4th line is 1211 which describes (one 2, one 1). And so forth...
What's the Next Number?
Riddle:
2, 3, 5, 9, 17, _ What is the next number in the sequence?