Every so often its good to exercise your brain with a math problem or two that forces you to recall principles you learned decades prior. Can you solve 5+5x5+5 without a hitch?

What seemed like a regular grade school math problem had people totally stumped on social media.

Both of those seem high to me, since the sum of the first 10^6 terms of the series is < 137 and the terms get smaller as they progress.