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## 1, 3, 6, 55, 66...

 Category: Series Submitted By: fishmed Fun: (2.2) Difficulty: (3.13)

What are the next three numbers in this series?

1, 3, 6, 55, 66, 171, 595, 666, 3003, 5995, ?, ?, ?

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Comments on this teaser

 Posted by swordflame 12/02/04 For those people who don't know what a triangular number is, http://mathworld.wolfram.com/TriangularNumber.html is a very nice introduction (helped me anyway). Posted by Nicky101 12/07/04 Thanx, I'll go there :D Posted by i_am_hated 04/13/05 me too...eventually ^_^ Posted by Nicholle 04/21/05 I still don't get it. :-? Posted by deadeye823 04/26/05 wow...the hardest teaser on the site Posted by darthforman 05/11/05 :( it IS the hardest... :lol: 8) Posted by KimOHara 05/21/05 I got the triangular part right away, but couldn't get the other part... the EASY part, now that I know what it was! Posted by lessthanjake789 06/01/05 i got the palindromic triangle part, but dont know how to figure out triangle numbers, and wasnt sitting there for a LONG LONG time doing them and checking for palindrom-icity (yes, i made that word up) Posted by triskit 06/02/05 i didnt get it :cry: Posted by Question_Mark 06/11/05 WOW! THAT IS HARD! :roll: :( :cry: Posted by brianz 06/11/05 I realized they were all triangular numbers but couldn't figure out the correlation between them. Nice teaser, I don't think it is so hard. :D Posted by Llama-Llover 09/22/05 :roll: Orangutans forced to watch Days Of Our Lives could have aced that one. Try and think of something harder next time. :roll: Posted by hamburger 10/02/05 I got the palindrome part, ( Didnt everyone :lol: ) But I didnt see the triangular part right away.This was very hard! Posted by schatzy228 10/09/05 WOW!, needed 2nd cup of coffee and 40yrs of memory back to high school, but it finally came to me GREAT JOB 8) Posted by bamfan 10/24/05 con grats on the hardest teaser p.s. did any one get it right Posted by smarty_blondy 11/07/05 Hardest one on site? I got this one right away as i knew half of them and so i got the pattern. Only had to do a bit of googling for the missing ones. I will admit it's brilliant though, good job! :D Posted by mrbrainyboy 12/06/05 :o don't get it... :( 8) Posted by trickyone 01/02/06 I got tha palindrome part but only got the triangular number part after the hint Posted by tolkienfan27 05/10/06 :-? Posted by MalcolmReynolds 10/12/06 Heh .. I was trying to work out a pattern before I realized they were palindromic. Lol................. 1,3,6,10,55,66,171 corresonds with 1,2,3,10,11,18... Okay, maybe it's 123, 123... 1+0=1... 1+1= 2... 1+8=.. damn. Didn't want to go down the line calculating.. so I googled palindromic triangular numbers :P Posted by Dan141 11/14/06 Easy, just simple....Not its the hardest one here :-? Posted by javlad27 07/28/07 what's a triangular number? :-? Posted by javaguru 01/08/09 Took longer to figure out what the next three palindromic triangular numbers were than it did to figure out the rule. Pretty nice teaser, but not terribly difficult. 8) Posted by Photon 03/09/09 I don't understand why this one is rated so difficult? Posted by krishnan 09/01/10 Nice, fun teaser, got the answer as soon as I saw 55 and 66.

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