This article discusses the two incarnations of Otter entered in the CADE-13 Automated Theorem Proving Competition. Also presented are some historical background, a summary of applications that have led to new results in mathematics and logic, and a general discussion of Otter.

this article we report the fact that a shorter and more intuitive formula can be used to constructively replace von Plato's Axiom 4.3, the third axiom of compatibility of equality with apartness and convergence. This result was obtained after many computer experiments using our prover ANDP. 2 Description of ANDP