This was the last book published by Euler in his lifetime in 1783, and consists of a number of papers presented to the St. Petersburg Academy of Sciences. A general summary of this work can be found in Ronald S. Calinger's Leonhard Euler, pp. 529-30. It should be observed that such works were not written to educate aspiring mathematicians, as were his calculus and analytical books, but rather took the form of what we would now call research papers.
Click here for the 1st Chapter [E550]: On series in which the products from two contiguous terms constitute a given progression.
This is rather a long paper, in which two methods are introduced for finding the general term of a special kind of series of the form a, ab, bc, cd, de, etc. , where the series or rather sequence has the terms designated by A, B, C, D, etc., where the first term a may not be known initially. This gives rise to solutions in terms of infinite products that may be solved either by integrals [E223] , or by continued fractions , originally investigated in E122. Most of the work consists of setting up products of quadratic equations of various kinds which can be recast as continued fractions, using the comparison of coefficients to show how this is done in these cases.
Click here for the E19 :
Click here for the E122 : Concerning transcendental progressions, or of which the the general terms are unable to be given algebraically.
This again is rather a long paper, and depends on E19, on which it relies heavily, especially on the theorem in section 16 of that, where essentially infinite products are displayed as products of integrals. This work is a continuation of that, and is difficult at times due to the lack of decent notations.
Click here for the 2nd Chapter [E551] : Various method of enquiring into the nature of series.
This is rather quite a short paper and quite delightful; it sets out to form the sum of the series to be found from middle maximum terms of expansions of the trinomial (1+x+x2)n with n, starting from an inductive proof which is fallacious; then the genius who was Leonhardt Euler takes over ……
Click here for the 3rd Chapter [E552]: Observations regarding the division of squares by prime numbers.
This is also rather a short paper, in which Euler inducts the reader into the charm of remainders or residues of squares divided by prime numbers, which laid the foundations for further work, especially in Gauss's masterful treatment in his Disquisitiones Arithmeticae. See e.g. D. J. Struik's A Source Book in Mathematics, 1200-1800 (1969, Harvard University Press), pp. 40-46.
Click here for the 4th Chapter [E553]: Analytical observations regarding continued fractions.
This is a longer paper, and one on which it appears Euler spent some time; in it he considers two related kinds of continued fractions, and establishes transformations between the two.
Ian Bruce. June. 21th , 2017 latest revision. Copyright : I reserve the right to publish this translated work in book form. You are not given permission to sell all or part of this translation as an e-book. However, if you are a student, teacher, or just someone with an interest, you can copy part or all of the work for legitimate personal or educational uses. See note on the index page.Please feel free to contact me if you wish by clicking on my name here, especially if you have any relevant comments or concerns.