Newsgroups: sci.math
From: W^3 <aderamey.a...@comcast.net>
Date: Tue, 03 Nov 2009 22:21:06 -0800
Local: Wed, Nov 4 2009 6:21 am
Subject: Re: Cauchy condensation test handout
In article
<787955160.5424.1257286864665.JavaMail.r...@gallium.mathforum.org>, master1729 <tommy1...@gmail.com> wrote: That's false: Take g(n) = 2n^2 and a_n = 1/n^(3/2). Then sum a_n < oo, > Dave L Renfro wrote : > > The purpose of this post is to archive an old > > Dave L. Renfro > generalizations might be intresting. > tommy condensation test :) > 0 < a_n < a_n+1 > a0 + a1 + a2 + a3 + ... < oo <=> 2 a0 + 2 a2 + 2 a4 + ... < oo > x) > in general for rising g(n) E N and g'(n) > 1 > sum g(n)a_g(n) < oo <-> sum a_n < oo but sum g(n)a_g(n) = sum 2n^2/(2n^2)^(3/2) = oo. > e.g. False too, with the same example. > sum T(n)a_T(n) < oo <-> sum a_n < oo > with T(n) = triangular number. > but probably the cases a_n = oo <=> sum ??? = oo
> are the intresting ones. > im convinced earlier work has been done on such matters. > btw > (under trivial conditions) > sum f(n) = sum g(1/n) = sum a0 + a1 1/n + a2 1/n^2 + ... > = a0 + a1 zeta(1) + a2 zeta(2) + ... > and prove almost the entire case ( again under trivial conditions ) with the > but that is more complicated then neccassary. > also , i suppose you ( dave l renfro ) is already aware of the above. > and thus in a sense my post is more aimed at others. > i suspect the handout occured during taylor series radius of convergeance > i think there might be potential in applying multiple combinations of > is there a non-trivial relation to special functions worth mentioning ? > regards > tommy1729 You must Sign in before you can post messages.
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