#paperOfTheDay is "Disquisitiones Generales circa seriem infinitam" by Carl Friedrich Gauss 1812. Probably one of the most influential #mathematics publications of all times. Gauss introduces a certain class of infinite series -- today known as Gaussian hypergeometric series -- which describe a new class of transcendental functions, namely the Gaussian hypergeometric function. Essentially all other transcendental functions known at that time are special cases of it. Gauss proves numerous properties and identities, including the relation to the Euler gamma function, and new identities for it. Also, he introduces the concept of contiguous relations (which today are a workhorse of perturbative #quantumFieldTheory under the name "IBP-relations"). He also comments on the monodromy arising when the function is being continued around one of the singular points of the differential equation.
I have read the German translation from 1888, which I find surprisingly clear and easy to follow. There is essentially no technical language (because Gauss was decades ahead of the community), but instead simple explicit calculations that any student can follow, and which lead to deep conclusions when interpreted cleverly. #dailyPaperChallenge https://gdz.sub.uni-goettingen.de/id/PPN35283028X_0002_2NS