Abstract: The method of "condensation", due to Charles Dodgson (Lewis Carroll), gives a method of computing determinants using a certain nonlinear recurrence relation. David Robbins discovered that using condensation, together with a p-adic analogue of floating point arithmetic, produced unusually accurate computations of determinants. Robbins formulated a precise conjecture to this effect, which remains open. We will describe Robbins's observations, speculate on possible generalizations to other nonlinear recurrences with "unexpected integrality" properties, and prove that Robbins's phenomenon manifests in a particular special case (the Conway-Coxeter "number friezes").