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Ponder This

July 2001

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Ponder This Challenge:

Find an exact expression for the infinite sum:


    1/1 + 2/(2+3) + 3/(4+5+6) + 4/(7+8+9+10) + ...

By "exact expression", I mean that "sqrt(2)" would be accepted
(if that were the right answer) but "1.414..." would not.

(This problem was posed by Saradakanta Ganguli, a long time ago.)


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Challenge: 07/02/01 @10:30 AM EST
Solution: 07/31/01 @2:00 PM EST
List Updated: 07/25/01 @2:30 PM EST

People who answered correctly:

Henry Bottomley (07.02.2001 @ 12:37 PM EDT)

Vince Lynch (07.02.2001 @ 12:57 PM EDT)
Vladimir Sedach (07.02.2001 @ 1:43 PM EDT)
Michael Malak (07.02.2001 @ 2:28 PM EDT)
Tamas Visegrady (07.02.2001 @ 10:46 PM EDT)
Stephane Higueret (07.03.2001 @ 3:37 AM EDT)
Arjun Viswanathan (07.02.2001 @ 7:01 AM EDT)
Prabhat Agarwal (07.03.2001 @ 8:03 AM EDT)
Saibal Mitra (07.03.2001 @ 9:04 AM EDT)
Patrice De Pra (07.03.2001 @ 10:05 AM EDT)
Duncan Murphy (07.03.2001 @ 10:14 AM EDT)
Ross Millikan (07.03.2001 @ 1:07 PM EDT)
Dave Biggar (07.03.2001 @ 2:15 PM EDT)
Danny Yuan (07.03.2001 @ 2:53 PM EDT)
Vinko Marinkovic (07.03.2001 @ 5:36 PM EDT)
Nancy Schwarzkopf (07.03.2001 @ 10:03 PM EDT)
Diego M.S. Erdody (07.04.2001 @ 12:42 AM EDT)
Jes˙s Gago-Vargas (07.04.2001 @ 3:19 AM EDT)
Jan van Delden (07.04.2001 @ 10:04 AM EDT)
Rich Bauer (07.04.2001 @ 4:27 PM EDT)
Karthik Narayanan (07.04.2001 @ 9:07 PM EDT)
Mark Pilloff (07.04.2001 @ 9:25 PM EDT)
Jayavel Sounderpandian (07.04.2001 @ 9:34 PM EDT)
George Ross (07.04.2001 @ 11:40 PM EDT)
Jean-Franšois Peltier (07.05.2001 @ 5:49 AM EDT)
Dharmashankar Subramanian (07.05.2001 @ 7:20 AM EDT)
Philippe Fondanaiche (07.05.2001 @ 5:11 PM EDT)
Nagendra (07.06.2001 @ 5:33 AM EDT)
Jacques Willekens (07.06.2001 @ 8:05 AM EDT)
Darryl Buller (07.06.2001 @ 8:29 AM EDT)
Mac Cornes (07.06.2001 @ 9:37 AM EDT)
Samantha Levin (07.06.2001 @ 1:38 PM EDT)
Avnish Miduthuri (07.06.2001 @ 5:54 PM EDT)
Yoshi Takimoto (07.07.2001 @ 5:41 AM EDT)
L Shankar Ram (07.07.2001 @ 7:32 AM EDT)
S V Nagaraj (07.09.2001 @ 4:24 AM EDT)
Prithu (07.09.2001 @ 7:54 AM EDT)
D Bizzarri (07.09.2001 @ 11:19 AM EDT)
Andrea Kung (07.09.2001 @ 2:20 PM EDT)
Jack Kennedy (07.10.2001 @ 7:11 PM EDT)
Victor Chang (07.10.2001 @ 8:03 PM EDT)
Alec Klatchko (07.10.2001 @ 8:52 PM EDT)
Dwight Divine (07.11.2001 @ 5:24 PM EDT)
Maverick Woo (07.11.2001 @ 8:38 PM EDT)
Itsik Horovitz (07.12.2001 @ 2:40 AM EDT)
Liuwei (07.12.2001 @ 11:17 AM EDT)
William Accad (07.03.2001 @ 3:56 AM EDT)
Blake Thornton (07.13.2001 @ 1:03 PM EDT)
Andrew Scherbakov (07.13.2001 @ 5:11 PM EDT)
Yuqing Deng (07.15.2001 @ 3:54 PM EDT)
Martin Gasevski (07.15.2001 @ 7:43 PM EDT)
Johan Alfredsson (07.16.2001 @ 1:59 PM EDT)
Pritibhushan Sinha (07.17.2001 @ 10:33 AM EDT)
Eric Hudson (07.18.2001 @ 11:41 AM EDT)
Sudipta Das (07.18.2001 @ 11:55 AM EDT)
Francisco Coelho (07.18.2001 @ 12:26 PM EDT)
Michal Kvasnicka (07.20.2001 @ 7:00 AM EDT)
Oluwamuyiwa Olubuyide (07.20.2001 @ 11:37 AM EDT)
Surendar Nanchary (07.20.2001 @ 2:44 PM EDT)
Michael Webb (07.20.2001 @ 3:13 PM EDT)
Derrick N Hart (07.20.2001 @ 10:47 PM EDT)
Alan Saw (07.21.2001 @ 12:14 AM EDT)
Sriram Srinivasan (07.21.2001 @ 3:20 PM EDT)
Padmasundari Gopalakrishnan (07.23.2001 @ 1:32 AM EDT)
Gururaj Alagwadi (07.23.2001 @ 2:37 AM EDT)
Christopher Hiszpanski (07.23.2001 @ 10:02 PM EDT)
Andrew Byde (07.24.2001 @ 1:53 PM EDT)
Bill Webb (07.25.2001 @ 10:44 PM EDT)
Amites Sarkar (07.27.2001 @ 10:40 AM EDT)
Imtiaz Hossain (07.27.2001 @ 4:13 PM EDT)
G.V.R. Anand (07.31.2001 @ 12:07 PM EDT)
Sarah Travers (07.31.2001 @ 1:38 PM EDT)


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