Mike, as I said, you should register with the OEIS - then you can propose edits to entries yourself 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 2:33 PM, Mike Speciner <ms@alum.mit.edu> wrote:
Your definition of "arrangement" does not seem to be a standard one...
Wolfram: In general, an arrangement of objects is simply a grouping of them. The number of "arrangements" ofnitems is given either by acombination <http://mathworld.wolfram.com/Combination.html>(order is ignored) orpermutation <http://mathworld.wolfram.com/Permutation.html>(order is significant).
Math Goodies: Arrangement numbers, more commonly called permutation numbers, or simply permutations, are the number of ways that a number of things can be ordered or arranged.
On 08-May-15 13:25, Joerg Arndt wrote:
I think the old definition was OK: the "arrangements of a set S" are (for me) all permutations of all subsets of S. So "arrangements of the subsets of S" would be something different (and quite contrived).
Rationale: if "arrangement" is the same as "permutation" then it is redundant terminology. Let us agree it's not (even if perhaps old-fashioned) and restore the old NAME of A000522.
Best regards, jj
* Neil Sloane <njasloane@gmail.com> [May 08. 2015 19:15]:
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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