Integral Recurrences from A to Z

By Robert Dougherty-Bliss


Appeared in The American Mathematical Monthly (circa 2022)

George Boros and Victor Moll’s masterpiece Irresistible Integrals does well to include a suitably-titled appendix, “The Revolutionary WZ Method,” which gives a brief overview of the celebrated Wilf-Zeilberger method of definite summation. Paradoxically, Irresistible Integrals does not contain the suitably-titled appendix, “The Revolutionary AZ Method,” which would have been an excellent place to give a brief overview of the Almkvist-Zeilberger method of definite integration! This omission can be forgiven, but once realized it must be rectified. The remarkable AZ machinery deserves to be more widely known to the general public than it is. We will do our part by presenting a series of case studies that culminate in a - fun but overkill - integral-based proof that e is irrational.