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 mared November 14th, 2014 08:59 PM

complete

3 , 3 , 9 , 5 , 16 , ...........

 Denis November 14th, 2014 10:24 PM

Quote:
 Originally Posted by mared (Post 212719) 3 , 3 , 9 , 5 , 16 , ...........
3,3,9,5,16,a
where a = anything you want :ninja:

 tahirimanov November 15th, 2014 12:31 AM

May be, it is 4,3,9,5,16?????

 Denis November 15th, 2014 03:38 AM

Quote:
 Originally Posted by tahirimanov (Post 212730) May be, it is 4,3,9,5,16?????
You forgot the comma after 16 :mask:

 Math Message Board tutor November 15th, 2014 06:27 AM

Quote:
 Originally Posted by tahirimanov (Post 212730) May be, it is 4,3,9,5,16?????
Your first number is different from the first number in the original poster's sequence.

 tahirimanov November 15th, 2014 09:10 AM

Quote:
 Originally Posted by Denis (Post 212746) You forgot the comma after 16 :mask:
******************

Quote:
 Originally Posted by Math Message Board tutor (Post 212760) 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.

 soroban November 15th, 2014 09:29 AM

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.

 Denis November 15th, 2014 09:45 AM

Quote:
 Originally Posted by tahirimanov (Post 212771) 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.:ninja:
Wish I could use the "thanks" button twice...

 Math Message Board tutor November 15th, 2014 10:15 AM

Quote:
 Originally Posted by tahirimanov (Post 212771) ****************** 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 (Post 212773) Wish I could use the "thanks" button twice...
Well, you can't use it twice. Your "thanks" were misguided as was pointed out above.