### Brain Teasers

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

What are the next three numbers in this series?

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

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

### Hint

3-sides### Answer

8778, 15051, 66066These are the 1st 13 palindromic triangular numbers.

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## Comments

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).

Thanx, I'll go there

me too...eventually ^_^

I still don't get it.

wow...the hardest teaser on the site

it IS the hardest...

I got the triangular part right away, but couldn't get the other part... the EASY part, now that I know what it was!

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)

i didnt get it

WOW! THAT IS HARD!

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.

Nice teaser, I don't think it is so hard.

Orangutans forced to watch Days Of Our Lives could have aced that one. Try and think of something harder next time.

I got the palindrome part, ( Didnt everyone ) But I didnt see the triangular part right away.This was very hard!

Oct 05, 2005

I learned triangular numbers in year 7 EASY

WOW!, needed 2nd cup of coffee and 40yrs of memory back to high school, but it finally came to me GREAT JOB

con grats on the hardest teaser

p.s. did any one get it right

p.s. did any one get it right

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!

don't get it...

I got tha palindrome part but only got the triangular number part after the hint

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

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

Easy, just simple....Not its the hardest one here

what's a triangular number?

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.

Pretty nice teaser, but not terribly difficult.

I don't understand why this one is rated so difficult?

Nice, fun teaser, got the answer as soon as I saw 55 and 66.

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