I have a vector:

```
> dput(rn, 20)
c(128L, 241L, 354L, 467L, 580L, 693L, 806L, 919L, 1032L, 1145L, 
1258L, 1371L, 1484L, 1597L, 1710L, 1823L, 1936L, 2049L, 2162L, 
2275L)

```

How do I get every third record from this vector?