A classical result of Erdős, Lovász and Spencer from the late 1970s asserts that the dimension of the feasible region of homomorphic densities of graphs with at most k vertices in large graphs is equal to the number of connected graphs with at most k vertices. Glebov et al. showed that pattern densities of indecomposable permutations are independent, i.e., the dimension of the feasible region of densities of k-patterns is at least the number of non-trivial indecomposable permutations of size at most k. We identify a larger set of permutations, which are called Lyndon permutations, whose pattern densities are independent, and show that the dimension of the feasible region of densities of k-patterns is equal to the number of non-trivial Lyndon permutations of size at most k.