# Generate a function from a list of numbers

1. Jul 14, 2014

### chipChocolate

I have a list of numbers x = [1, 11, 21, 1211, 111221,...], I need to find the 31st number in that list.

2. Jul 14, 2014

### micromass

Staff Emeritus
Hint: Look and say

Hint 2: 11 should not be seen as "eleven" but rather as individual ones.

3. Jul 14, 2014

### pasmith

It could be anything. Truncating a sequence loses all information about subsequent terms.

Are you told how to construct the $n$th term, given the values of previous terms? If so, you need to do that.

4. Jul 14, 2014

### chipChocolate

The actual question is to find the length of the 31st term.

Last edited: Jul 14, 2014
5. Jul 14, 2014

### micromass

Staff Emeritus
You need to recognize the pattern first. See Post #2.

6. Jul 14, 2014

### xiavatar

Hint: The next term says something, quite literally, about the previous term.

7. Jul 14, 2014

### chipChocolate

Thanks for the hint, I finally got it.

8. Jul 14, 2014

### HakimPhilo

The problem with this type of questions is that they have more than one answer in general. For this particular sequence we have 3 possibilities that can be found at OEIS.