## I don't know what this symbol meansgreenspun.com : LUSENET : Lexington High School Mathematics : One Thread |

Alright, I'm doing this project on Catalan number systems, and one of the formulas involved is this: (2N) N ____ N+1 The 2N is directly over the N, and they are both in the parentheses (that's not what it looks like, but it should look like that). So what does that mean? What operation?

-- Adrian Martin (a_d0gg@myrealbox.com), May 27, 2001

it is from combinatorics. it mean out of 2N choose N. I believe the formula for this is 2N! / [(2N-N)! * (N!)] which simplifies to 2N! / (N!)^2 .

-- Mr. Richardson (wrichardson@sch.ci.lexington.org), September 26, 2001.

of cousre i mistyped my e-mail address sorry

-- Mr. Richardson (wrichardson@sch.ci.lexington.ma.us), September 26, 2001.

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