This article explains breadth first traversal and depth first traversal in graph theory.
Terminology and methods to represent a graph are explained.
Segmented Sieve, Sieve of Sundaram, Sieve of Atkin are discussed here.
A more optimized approach to the use of recursion
Recursion vs Iteration, which is better? This article will go through pros/cons of iteration and recursion.
Introduction to the concept of Recursion