### creating a polynomial ring

The following ~~code produces an error the following
n=4
k=n*(n-1)/2
L=PolynomialRing(ZZ,k,"x")~~code

```
n=4
k=n*(n-1)/2
L=PolynomialRing(ZZ,"x",k)
```

produces the following error

`if second arguments is a string with no commas, then there must be no other non-optional `~~arguments... ~~arguments...

If I replace k by 6 or binomial(n,2) everything works, I cannot understand why. Thanks for any help