A bijective approach to the area of generalized Motzkin paths

  • Authors:
  • E. Pergola;R. Pinzani;S. Rinaldi;R. A. Sulanke

  • Affiliations:
  • Dipartimento di Sistemi e Informatica, Università di Firenze, Florence, Italy;Dipartimento di Sistemi e Informatica, Università di Firenze, Florence, Italy;Dipartimento di Sistemi e Informatica, Università di Firenze, Florence, Italy;Boise State University, Boise, Idaho

  • Venue:
  • Advances in Applied Mathematics - Special issue: Memory of Rodica Simon
  • Year:
  • 2002

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Abstract

For fixed positive integer k, let En denote the set of lattice paths using the steps (1, 1), (1, -1), and (k, 0) and running from (0, 0) to (n, 0) while remaining strictly above the x-axis elsewhere. We first prove bijectively that the total area of the regions bounded by the paths of En and the x-axis satisfies a four-term recurrence depending only on k. We then give both a bijective and a generating function argument proving that the total area under the paths of En equals the total number of lattice points on the x-axis hit by the unrestricted paths running from (0, 0) to (n - 2, 0) and using the same step set as above.