A Gel'fond type criterion in degree two
Very recently, the generating function of the Stern sequence , defined by and for any integer , has been considered from the arithmetical point of view. Coons [8] proved the transcendence of for every algebraic with , and this result was generalized in [6] to the effect that, for the same ’s, all numbers are algebraically independent. At about the same time, Bacher [4] studied the twisted version of Stern’s sequence, defined by and for any .The aim of our paper is to show...
In his proof of Apery’s theorem on the irrationality of , Beukers [B] introduced double and triple integrals of suitable rational functions yielding good sequences of rational approximations to and . Beukers’ method was subsequently improved by Dvornicich and Viola, by Hata, and by Rhin and Viola. We give here a survey of our recent results ([RV2] and [RV3]) on the irrationality measures of and based upon a new algebraic method involving birational transformations and permutation groups...