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 November 14th, 2014, 08:59 PM #1 Senior Member   Joined: Nov 2013 Posts: 434 Thanks: 8 complete 3 , 3 , 9 , 5 , 16 , ...........
November 14th, 2014, 10:24 PM   #2
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Quote:
 Originally Posted by mared 3 , 3 , 9 , 5 , 16 , ...........
3,3,9,5,16,a
where a = anything you want

 November 15th, 2014, 12:31 AM #3 Senior Member     Joined: Nov 2013 From: Baku Posts: 502 Thanks: 56 Math Focus: Geometry May be, it is 4,3,9,5,16?????
November 15th, 2014, 03:38 AM   #4
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Quote:
 Originally Posted by tahirimanov May be, it is 4,3,9,5,16?????
You forgot the comma after 16

November 15th, 2014, 06:27 AM   #5
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Quote:
 Originally Posted by tahirimanov May be, it is 4,3,9,5,16?????
Your first number is different from the first number in the original poster's sequence.

November 15th, 2014, 09:10 AM   #6
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Quote:
 Originally Posted by Denis You forgot the comma after 16
******************

Quote:
 Originally Posted by Math Message Board tutor Your first number is different from the first number in the original poster's sequence.
Wow, how did you find it out?!!! It was my point, to ask mared if (s)he posted the problem correctly.

November 15th, 2014, 09:29 AM   #7
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Hello, mared!

I found a pattern . . .

Quote:
 $3,\;3 ,\;9 ,\;5 ,\;16\;\cdots$

$\begin {array}{c|ccccccccc} \hline a_n & 3 &&3&&9&&5&&16 \\ \hline \text{1st diff} && 0 && +6 && -4 && +11 \\ \hline \text{2nd diff} &&& +6 && -10 && +15 \\ \hline \end{array}$

The second differences are the 3rd, 4th and 5th Triangular Numbers
$\qquad$ with alternating signs.

November 15th, 2014, 09:45 AM   #8
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Quote:
 Originally Posted by tahirimanov Wow, how did you find it out?!!! It was my point, to ask mared if (s)he posted the problem correctly.
Your brilliance blinds me. What a simply elegant way to confuse the issue.
Wish I could use the "thanks" button twice...

Last edited by Denis; November 15th, 2014 at 09:48 AM.

November 15th, 2014, 10:15 AM   #9
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Quote:
 Originally Posted by tahirimanov ****************** Wow, how did you find it out?!!! It was my point, to ask mared if (s)he posted the problem correctly.
I found out by inspection! Your sarcasm doesn't count. It's null and void.
There's no reason here to assume the first number was/is off.

Quote:
 Originally Posted by Denis Wish I could use the "thanks" button twice...
Well, you can't use it twice. Your "thanks" were misguided as was pointed out above.

Last edited by Math Message Board tutor; November 15th, 2014 at 10:18 AM.

November 15th, 2014, 11:36 AM   #10
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Quote:
 Originally Posted by Math Message Board tutor Well, you can't use it twice. Your "thanks" were misguided as was pointed out above. Your "thanks" have been nullified.
Read my post again...it's the "opposite" of what I "typed"...

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