Talk:Kempner series

The importance of 9
It's been proven that the series converges if denominators containing any certain string are removed, 9 doesn't seem to have any special significance. Is there a reason it's treated specially in the article? — Preceding unsigned comment added by KingSupernova (talk • contribs) 06:38, 9 June 2016 (UTC)

I didn't write this article, but I would say it's primarily a historical reason: Kempner's original paper works through the proof for the 9 case. Also, the proof is easier to understand if the details are worked out using a definite digit, like 9. --MathPerson — Preceding unsigned comment added by MathPerson (talk • contribs) 12:58, 9 June 2016 (UTC)