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Category: | Series |

Submitted By: | fishmed |

Fun: | (2.21) |

Difficulty: | (3.12) |

What are the next three numbers in this series?

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

Show Hint | Show Answer |

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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