On a nonorthogonal polynomial sequence associated with Bessel operator
  By means of the Bessel operator a polynomial sequence is constructed to which several properties are given. Among them, its explicit expression, the connection with the Euler numbers, its integral representation via the Kontorovich-Lebedev transform. Despite its non-orthogonality, it is possible to associate to the canonical element of its dual sequence a positive-definite measure as long as certain stronger constraints are imposed. 
Ana F. Loureiro, P. Maroni, S. Yakubovich
math.CA