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 !