hi everyone

Compute $\displaystyle S_5$for the following:

$\displaystyle \sum^\infty _{n=0} a_n$ if $\displaystyle a_n=n(n+1)(n+2)$

my working:

start from a1= 0=0(0+1)(0+2)=0

a2=1=1(1+1)(1+2)=6

a3=2=2(2+1)(2+2)=24

a4=3=3(3+1)(3+2)=60

a5=4=4(4+1)(4+2)=120

answer :210

i am confused wheter the answer is 210 or 420. i started with a1(0) until a5(4).

i am confused,please advise. did i do it right,

thank you so much for your advice.

thank you in advance.