doc: add notes

Author: JCPedroza

algorithms-and-data-structures/project-euler/002-even-fibonacci-numbers/README.md

@@ -1,33 +1,44 @@
 # Project Euler 002 - Even Fibonacci Numbers
 
 Each new term in the Fibonacci sequence is generated by adding the previous
-two terms. By starting with 0 and 1, the first 10 terms will be:
+two terms. Starting with 0 and 1, the first 10 terms are:
 
 ```text
 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ...
 ```
 
 By considering the terms in the Fibonacci sequence whose values do not exceed
-`n`, find the sum of the even-valued terms.
+`limit`, find the sum of the even-valued terms.
 
-The function signature is
+## Function Signature
 
 ```typescript
 function fiboEvenSum(limit: int): int
 ```
 
+## Expected Behavior
+
+```
+In: -1
+Out: 0
+
+In: 0
+Out: 0
+
+In: 2
+Out: 2
+
+In: 10
+Out: 10
+
+In: 60
+Out: 44
+```
+
 ## Optimizations
 
 Trial division isn't necessary. There are ways to only compute even fibonacci
 numbers, including:
 
 - Every third number in the sequence is even
-- You can calculate only even members with `next fibo = 4 * next fibo + current fibo`
-
-## Resources
-
-- [Project Euler Problem 002][1]
-- [Project Euler Problem 002 at freeCodeCamp][2]
-
-[1]: https://projecteuler.net/problem=2
-[2]: https://www.freecodecamp.org/learn/coding-interview-prep/project-euler/problem-2-even-fibonacci-numbers
+- Calculating even values only with `next fibo = 4 * next fibo + current fibo`