feat(pascal): create README.md

Author: nik-rev

19_pascal/README.md

@@ -1,3 +1,18 @@
-# Exercise 17 - pascal
+# Exercise 19 - pascal
 
-Description of the exercise goes here.
+The pascal's triangle is modelled as follows:
+- The first row is `1`.
+- Each row can be considered to have a hidden `0` to either sides of it. So the first row could
+also be said to be `0, 1, 0`
+- To obtain the next row, we take each number and add it with its rightmost neighbor.
+
+First row: `[1]`
+Second row: `[0+1, 1+0]` or simply `[1, 1]`
+Third row: `[0+1, 1+1, 1+0]` or simply `[1, 2, 1]`
+Fourth row: `[0+1, 1+2, 2+1, 1+0]` or simply `[1, 2, 2, 1]`
+... 
+
+The pattern continues forever.
+
+Your task is to create a *recursive* function, `pascal` - that will take an input `n` and output the 
+`n`th pascal's row.