> permutation(letters[1:3])
[[1]]
[1] "c" "b" "a"

[[2]]
[1] "b" "c" "a"

[[3]]
[1] "b" "a" "c"

[[4]]
[1] "c" "a" "b"

[[5]]
[1] "a" "c" "b"

[[6]]
[1] "a" "b" "c"