Narayana number

Okay, kiddo. So Narayana number is a special type of number that helps us count different things. It's named after an Indian mathematician named Narayana who studied these numbers a long time ago.

Let's say you have some blocks and you want to build a tower. You can use the Narayana number to tell you how many ways you can build that tower.

The Narayana number formula looks like this: N_n = N_{n-1} + N_{n-2} * (n-1), where n is the number of blocks you have and N_n is the number of ways you can build a tower with those blocks.

Let's say you have 1 block. The Narayana number for 1 block is just 1, because there's only 1 way to build a tower with 1 block.

But let's say you have 2 blocks. The Narayana number for 2 blocks is also 1, because you can only build a tower by putting both blocks on top of each other.

Now, let's say you have 3 blocks. The Narayana number for 3 blocks is 2, because there are 2 ways to build a tower. You can either put one block on top of the other two, or you can put two blocks on top of the other one.

As you can see, the Narayana number tells us how many ways we can build a tower with a certain number of blocks. Pretty cool, huh?