Project Euler Problem 172

Posted in Mathematics

Overview: Problem 172

How many 18-digit numbers $$n$$ (without leading zeros) are there such that no digit occurs more than three times in $$n$$?

Link to Project Euler Problem 172

Background

Project Euler Problem 172 is your classic Project Euler problem: short, simple, and overwhelmingly complicated.

To nail this one, it's important to start simple - very simple. What I'll do is walk through the process of …

Posted in Mathematics

Overview: The Problem

In an earlier post, I mentioned my efforts on Project Euler and the wide variety of problems there that can offer some profound mathematical insights.

Given that the first post covered problem #1, I thought it would be nice if the next problem cranked up the difficulty factor by an order of magnitude. Problem 502 is a very hairy combinatorics problem that required me to learn about a wide variety of combinatorial enumeration techniques.

Project Euler Problem 1

Posted in Mathematics