rmutations in lexicographic order starts with all the
permutations with the lowest index, 1, followed by all permutations
starting with the following index, 2, and so on. The permutations
starting by an index <em>i</em> are the permutations of the first <em>n</em>
integers different from <em>i</em> and they are also placed in
lexicographic order, where the permutations with the lowest of those
integers are placed first and so on.
</p>
<p>See also <code><a href="#perm_005flex_005fnext">perm_lex_next</a></cod