A generalization of Chebyshev polynomials and non rooted posetsMasaya Tomie tomie@math.tsukuba.ac.jpIn this paper we give a generalization of Chebyshev polynomials and using this we describe the Mobius function of the generalized subword order derived from a poset {a 1 , · · · a s , c | a i < c f or i = 1, · · · s}, which contains an affirmative answer for the conjecture by Björner, Sagan and Vatter.(cf,[5] [10])