Here's what you might be thinking of:
* Pokemon Indigo League: This is the first season of the Pokemon anime, focusing on Ash Ketchum's journey through the Kanto region.
* Sinnoh Region: This is a region from the Pokemon video games, featured in the Pokemon Diamond, Pearl, and Platinum games. It's not a part of the anime's "Indigo League" storyline.
It's possible you're mixing up different aspects of the Pokemon franchise.
Can you clarify what you're looking for?
* Are you interested in the Gym Leaders Ash faced in the Indigo League?
* Are you interested in the Gym Leaders of the Sinnoh region in the video games?
* Are you asking about something else entirely?
Please provide more context so I can help you!