Re: Finding a formula for a sum
- To: mathgroup at smc.vnet.net
- Subject: [mg35134] Re: Finding a formula for a sum
- From: Samuel Kutter <sk256 at phy.cam.ac.uk>
- Date: Tue, 25 Jun 2002 19:55:12 -0400 (EDT)
- Organization: University of Cambridge, England
- References: <af97ij$2t$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hello I don't know how to guess sum-formulae by using mathematica given a series of integer numbers, but I would recommend using Mozilla and go to: http://www.research.att.com/~njas/sequences/index.html Sam On Tue, 25 Jun 2002 Matthias.Bode at oppenheim.de wrote: > Dear Colleagues, > > when trying to find the number of diagonals in a convex polygon (all corners > on the perimeter of a circle) with n corners I came across that sum: > > +(n-3) ; up to here = diagonals in a triangle. > > +(n-3) ; up to here = diagonals in a quadrangle. > > +(n-4) ; up to here = diagonals in a pentagon. > > +(n-5) ; up to here = diagonals in a hexagon. > > +(n-6) ; up to here = diagonals in a heptagon. > and so on. > > I found the general formula (n*n -3*n)/2 with pencil and paper. > > How could I coax MATHEMATICA into helping me to find the generalization in > this case - and of course for more difficult ones as well? >