Hey guys, just a quick query. The question says:

Find, as polynomials in n, the sum of

1.2.3 + 2.3.4 + ..... + n(n+1)(n+2)

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Is that simply

$\displaystyle \Sigma_{k=1}^{n} k(k+1)(k+2) = \Sigma_{k=1}^{n} k^3 + 3 \Sigma_{k=1}^{n} k^2 + 2 \Sigma_{k=1}^{n} k $

which, skipping through the steps is:

$\displaystyle \frac{1}{4}n(n+1)(n+2)(n+3) $

This is what they're asking for, aren't they?