Can you count and say what characters the string '11121' has?

It has three '1' characters, followed by one '2', and finally one '1'. Or to put it another way, it has 3 1s, 1 2s and 1 1, which we could write as the string '311211'. For this problem, we define this transformation as "counting and saying". Counting and saying '11121' is '311211'.

For this problem, you have to generate a sequence given an Integer N. We define base case for N = 1 as '1'. For N > 1, count and say the sequence generated by N - 1.

Examples:

countAndSay(1) == '1' // base case
countAndSay(2) == '11' // previous sequence has one 1.
countAndSay(3) == '21' // previous sequence has two 1s
countAndSay(4) == '1211' // previous sequence has one 2, one 1
countAndSay(5) == '111221' // ... and so on
countAndSay(6) == '312211'
countAndSay(7) == '13112221'

Write a function that takes N (sequence number) as a parameter and outputs the Nth sequence. 1<= N <= 20