De Bruijn's combinatorics

ak+1 algorithm arrows Assume augmenting path bijection binary tree bipartite graph bricks a1 Cauchy-Frobenius chain without repeated choose coefficient cograph color patterns column combinatorics complete set connected Consider corresponds count cube cycle index cycle of length cyclic d₁ define dotted elements endpoint equivalence classes equivalence relation Euler circuit Euler graph Euler paths exactly example Figure finite flow formal power series formula graph G infinite lemma Let G linegraph look losing position louse M-augmenting mapping Mathematics matrix move multiple multiset N. G. de Bruijn N₁ node number of trees oriented graph out-degree P₁ pairs perfect matching permutation plane stemtree player Pólya power series problem Proof prove rotations run-out S₁ sequence set of points Show spanning trees subset super patterns Theorem theory threshold graph UD-code vertex vertices weight words write zero Σ Σ