[r] How to combine two lists in R

I have two lists:

l1 = list(2, 3)
l2 = list(4)

I want a third list:

list(2, 3, 4).

How can I do it in simple way. Although I can do it in for loop, but I am expecting a one liner answer, or maybe an in-built method.

Actually, I have a list:
list(list(2, 3), list(2, 4), list(3, 5), list(3, 7), list(5, 6), list(5, 7), list(6, 7)).
After computing on list(2, 3) and list(2, 4), I want list(2, 3, 4).

I was looking to do the same thing, but to preserve the list as a just an array of strings so I wrote a new code, which from what I've been reading may not be the most efficient but worked for what i needed to do:

combineListsAsOne <-function(list1, list2){
  n <- c()
  for(x in list1){
    n<-c(n, x)
  }
  for(y in list2){
    n<-c(n, y)
  }
  return(n)
}

It just creates a new list and adds items from two supplied lists to create one.

We can use append

append(l1, l2)

It also has arguments to insert element at a particular location.