Is there a word for this?

Laying in bed last night I was trying to sleep and doing math in my head to help. I don't know how to explain this, but I'll try.

So, 10=10+9+8+7+6+5+4+3+2+1 then 10=55.

Or, 6=6+5+4+3+2+1 then 6=21

Or 8=8+7+6+5+4+3+2+1 then 8=36

And so on...

I couldn't figure out how to Google this, but I was wondering if this had a name, or if it is used for anything. It definitely helped me sleep, haha, so there's that!

Author: Sea_Beach3933