Mike, Adam - thanks! I will modify the defn. Mike - you should register with the OEIS, then we could remove your email address from your 2003 submission! Best regards Neil Neil J. A. Sloane, President, OEIS Foundation. 11 South Adelaide Avenue, Highland Park, NJ 08904, USA. Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ. Phone: 732 828 6098; home page: http://NeilSloane.com Email: njasloane@gmail.com On Fri, May 8, 2015 at 11:15 AM, Adam P. Goucher <apgoucher@gmx.com> wrote:
How are we defining 'arrangement'? This seems to be counting the number of tuples of distinct elements from an n-element set.
Sent: Friday, May 08, 2015 at 3:46 PM From: "Mike Speciner" <ms@alum.mit.edu> To: math-fun <math-fun@mailman.xmission.com> Subject: [math-fun] Sloane sequence A000522
This sequence is listed as Total number of arrangements of a set with n elements: a(n) = Sum_{k=0..n} n!/k!. But isn't the total number of arrangements of a set with n elements n! ? Isn't A000522 really the total number of arrangements of subsets of a set with n elements?
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