Ah word puzzles…
For this challenge, the most significant part is picking up on the sequence. After that, the solution can be reached through a straightforward loop with a check related to the sequence. The puzzle is more about the thought behind a process than learning to use a specific library.
From the source, we’re given the first elements of a sequence.
1, 11, 21, 1211, 111221,
Having seen this type of sequence before, it happened to seem easy – not the case for a couple friends of mine and it definitely sparked an interesting discussion about how different people who are good at recognizing patterns go about that process of discovery. If you’re stuck, I recommend reading the sequence aloud.
As for the code to solve the sequence:
import StringIO a = ['1'] for i in range(30): n = a[-1]+'?' next =  start = 0 for end in range(len(n)): if n[end] != n[start]: next.append(str(end-start)+ n[start]) start = end a.append(''.join(next)) print len(a[-1])