general term

Find the general term of this sequence ,

0 , 5 , 6 , 11 , ...

i can see the pattern +5 , +1 , +5 , ...

So i hv this idea ..

$\displaystyle 3+(-1)^r(2) $

where

$\displaystyle U_1=0 $
$\displaystyle U_2=U_1+3+(-1)^r(2)$ , where r=2
$\displaystyle U_3=U_2+3+(-1)^r(2) $, where r=3

And so on ..

$\displaystyle
U_n=U_{n-1}+\sum^{n}_{r=1}[3+(-1)^r(2) ]
$

I am not sure how to continue .. Am i on the right track . Thanks !

Maybe a better way might be to add the amount 3 - 2*(-1)^n at the n-th step...? (Wondering)

Quote:

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Originally Posted by stapel

Maybe a better way might be to add the amount 3 - 2*(-1)^n at the n-th step...? (Wondering)

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I don understand what you are trying to say .. Can you verify whether i am on the right track and the steps for me to continue .. Thanks .