ELI5: Explain Like I'm 5

Schröder–Hipparchus number

The Schröder-Hipparchus number is a special type of number that helps us count how many different ways we can arrange a set of objects in a certain pattern. Imagine you have some toys, like balls and blocks, and you want to stack them up in different ways. The Schröder-Hipparchus number helps us figure out how many different ways we can stack them.

Now, let's imagine we have two different sets of toys, one with 3 balls and one with 2 blocks. We want to stack them up together. The Schröder-Hipparchus number helps us figure out how many different ways we can stack them.

To do this, we use a special formula that takes into account the number of toys we have and how many we want to use in each stack. The formula looks like this: S(n) = S(n - 1) + S(n - 2) + 2 * (n - 1) * S(n - 1), where "n" is the total number of toys we have.

When we use this formula for our 3 balls and 2 blocks, we get a Schröder-Hipparchus number of 11. This means there are 11 different ways we can stack the toys together.

So, the Schröder-Hipparchus number is a special type of number used to count the number of different ways objects can be arranged in a pattern, using a special formula.