
Triangular numbers (Euler 11)
What’s a triangular number? It is the sequence found by summing all the natural numbers, for example the third number is $1+2+3=6$. Interestingly, it counts objects arranged as a triangle. This also has closed form $T_n=\sum_{i=1}^{n}i=\frac{n(n+1)}{2}$. I started with a brute force approach – iterate through the triangular numbers and test if the number of divisors […]