Sumatory formula

Question

Anybody knows the formula for this, because I don't know how to write it from the basic formula of $$\frac{n(n+1)}{2}$$:

$$\sum _{i=1}^{n}{ \sum _{j=1}^{ n}{ \sum _{ k=1 }^{ n }{ \sum _{ h=1 }^{ n }{ijkh}}}}$$

Thanks

Answer 1

Since the sums aren't dependent on the other variables we get

$$\sum_{i=1}^n\sum_{j=1}^n\sum_{k=1}^n\sum_{h=1}^n ijkh = \bigg(\sum_{i=1}^n i\bigg)\bigg(\sum_{j=1}^nj\bigg)\bigg(\sum_{k=1}^n k\bigg)\bigg(\sum_{h=1}^nh\bigg) = \bigg(\frac{(n)(n+1)}{2}\bigg)^4$$