Partially 2-colored permutations and the Boros–Moll polynomials

We find a combinatorial setting for the coefficients of the Boros–Moll polynomials Pm(a) in terms of partially 2-colored permutations. Using this model, we give a combinatorial proof of a recurrence relation on the coefficients of Pm(a). This approach enables us to give a combinatorial interpretation of the log-concavity of Pm(a) which was conjectured by Moll and confirmed by Kauers and Paule.