MathGroup Archive: January 2012 [00350]

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How to check whether an infinite set is closed under addition?

To: mathgroup at smc.vnet.net
Subject: [mg124277] How to check whether an infinite set is closed under addition?
From: Rex <aoirex at gmail.com>
Date: Sun, 15 Jan 2012 04:51:49 -0500 (EST)
Delivered-to: l-mathgroup@mail-archive0.wolfram.com

Given k positive numbers a_1<a_2<a_3<...<a_k, and all integers greater
than a_k, we want to check whether this set {a_1, a_2, a_3,...a_k, a_k
+ 1, a_k+2, ......} is closed under addition.

Is there any easy way to do this? any functions that we could use in
Mathematica?

Your help will be greatly appreciated.

Follow-Ups:
- Re: How to check whether an infinite set is closed under
  - From: DrMajorBob <btreat1@austin.rr.com>

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