@**article**{RISC3837,author = {Manuel Kauers and Christoph Koutschan and Doron Zeilberger},

title = {{Proof of Ira Gessel's Lattice Path Conjecture}},

language = {english},

abstract = { We present a computer-aided, yet fully rigorous, proof of Ira Gessel's tantalizingly simply-stated
conjecture that the number of ways of walking $2n$ steps in the
region $x+y \geq 0, y \geq 0$ of the square-lattice
with unit steps in the east, west, north, and south directions, that start and end at the origin, equals
$16^n\frac{(5/6)_n(1/2)_n}{(5/3)_n(2)_n}$ .},

journal = {Proceedings of the National Academy of Sciences},

volume = {106},

number = {28},

pages = {11502--11505},

isbn_issn = {ISSN 0027-8424},

year = {2009},

month = {July},

refereed = {yes},

length = {4}

}