Here is how I would do it. I would enter the episode number as the slug for your blog posts.
First, go to Settings, Permalinks. Choose the “Post name” option and click the “Save Changes” button. This does two things: It ensures that you will be able to pick a “slug” for your posts, and it prevents numbers in dates from interfering with your numeric slugs.
Next, you need to enter the slug for you blog posts. Let’s say you are creating a new blog post for episode 1, and the title of the post will be “Episode 1 Notes”. On the edit post screen, click on the Screen Options link at the top right corner of the screen. Then make sure that the “Slug” box is checked.
Once this is checked, then just below the box where you enter the title, you will see the URL for the post you are editing. This URL will end in something resembling your post’s title, such as “episode-1-notes”. This is called the slug. You want to change it to “1”, so click on the Edit button and change the slug to “1”. When you are done editing your post, click the “Publish” button (or “Update” button if you are editing an existing post).
Now, the URL of your post is http://example.com/1/, and you can tell people on the podcast that they can find the notes at “example dot com slash 1”.