Template:Did you know nominations/Ordered Bell number

Ordered Bell number

 * ... that because of the possibility of dead heats, the number of possible outcomes of a horse race is not a factorial, but an ordered Bell number?
 * Reviewed: David Kroyanker

Created by David Eppstein (talk). Self nominated at 03:36, 13 March 2013 (UTC).


 * I think it would be helpful to mathematically challenged readers such as myself if the Applications section of the article could be expanded to mention the application to races and state explicitly that where dead heats are not possible (can't think of an example) the number of outcomes is the factorial of the number of competitors. I know it's obvious, but people clicking to find a discussion of horse racing are going to be confused/disappointed. Espresso Addict (talk) 00:38, 15 March 2013 (UTC)
 * ✅. I didn't find a source for a kind of racing that disallows ties, but I did find a source with a different sports example (batting lineups), and I reused one of the existing sources for the difference in magnitude between these two types of number. —David Eppstein (talk) 01:17, 15 March 2013 (UTC)
 * Symbol confirmed.svg Thanks, that is an improvement. This seems to be essentially an expansion from a couple of sections in weak ordering; a back-of-the-envelope count of the DYK-able text suggests it is ~5-fold. Referencing appears adequate. The hook is interesting, under 200 characters, and supported by reliable references. It would probably be good to acknowledge the merge of some material from what is now weak ordering. I haven't checked the mathematical parts of this article, other than that they are cited, so if a qualified reviewer is available, feel free to re-review. Espresso Addict (talk) 01:55, 15 March 2013 (UTC)
 * Perhaps I should have mentioned that this is indeed a replacement for a former redirect to what is now in Weak ordering. However, I don't think I removed any text from that article (nor made much use of it in writing the new one). —David Eppstein (talk) 02:03, 15 March 2013 (UTC)