Skip to Content.
Sympa Menu

internetworkers - Re: [internetworkers] Math Problem

internetworkers AT lists.ibiblio.org

Subject: Internetworkers: http://www.ibiblio.org/internetworkers/

List archive

Chronological Thread  
  • From: Greg Cox <glcox AT pobox.com>
  • To: "Internetworkers: http://www.ibiblio.org/internetworkers/" <internetworkers AT lists.ibiblio.org>
  • Subject: Re: [internetworkers] Math Problem
  • Date: Fri, 25 Feb 2005 22:07:11 -0500 (EST)

> -- the number of unique combinations of N
> characters up to a sequence of N characters. for example, for 3 the
> answer is 39:
> 3 + 3^2 + 3^3 = 3 + 9 + 27 = 39
> because the unique combinations are A, B, C, AA, ...CC, AAA, ...CCC

X characters, strings of max N length, A = answer.


A = X + X^2 + X^3 + .... + X^(N-1) + X^N

XA = X^2 + X^3 + .... + X^(N-1) + X^N + X^(N+1)

XA - A = X^(N+1) - X

A(X-1) = X^(N+1) - X

A = (X^(N+1) - X) / (X-1)


Or, in your example of X=3, N=3:
A = (3^4 - 3) / 2 = (81 - 3) / 2 = 78/2 = 39






Archive powered by MHonArc 2.6.24.

Top of Page