perplexus.info :: Just Math : Two Geometric Series

Two Geometric Series (Posted on 2003-07-14)

Find a geometric series of 3 or more positive integers, starting with 1, such that its sum is a perfect square.

See if you can find another such series.

Submitted by Brian Smith

Rating: 3.6667 (6 votes)

Solution: (Hide)

Two such series 1,3,9,27,81 and 1,7,49,343 are solutions.
There are others.
1+3+3^2+3^3+3^4=121=11^2 and 1+7+7^2+7^3=400=20^2

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
Thoughts on the Problem	K Sengupta	2022-08-29 22:51:31
answer	K Sengupta	2007-11-08 09:53:58
re(2): Programming Solution	DJ	2003-07-15 05:41:05
re: Programming Solution	exoticorn	2003-07-14 22:41:33
Programming Solution	DJ	2003-07-14 18:10:12
after some quick programming...	exoticorn	2003-07-14 06:58:54
Halfway there	Bryan	2003-07-14 06:51:51
2 solutions	exoticorn	2003-07-14 06:48:05
Solution	Kyph	2003-07-14 06:46:14
Starters	DJ	2003-07-14 06:43:22
The Cheap Solution	Kyph	2003-07-14 06:37:02

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