**Wilhelm Ahrens** was a German mathematician best known for his work on recreational mathematics.

- Wilhelm was born in Lübz on the river Elde in northeast Germany, about halfway between Hamburg and Berlin.
- Ahrens passed his Master of Advanced Studies in Secondary and Higher Education in the 1895 and, in addition, he was awarded his Ph.D., summa cum laude (with the highest distinction), from the University of Rostock in the same year under the supervision of Otto Staude (1857-1928).
- Ahrens' 36-page thesis was entitled Über eine Gattung n-fach periodischer Functionen von n reellen Veränderlichen.
- Ahrens then spent a year teaching at the German School in Antwerp, before returning to university for a further year.
- After these university studies, Ahrens was employed at the School of Architecture for four years and later at the School of Mechanical Engineering in Magdeburg for three years.
- Giving up his career as a teacher, Ahrens relocated to Rostock as an independent scholar, in order to pursue his literary work.
- This book showed that Ahrens had an exceptionally thorough knowledge of the surrounding literature.
- One of the features of Ahrens' book, which distinguishes it from other similar books of the time, is that it is written for those who have some mathematical background and, consequently, he only looks at games which are mathematically interesting.
- In 1907 Ahrens published Mathematische Spiele Ⓣ(Mathematical Games) which was a shorter (only 118 pages) and much more elementary text on games which was intended to be instructive and entertaining reading for everyone.
- Ahrens did make changes to the book over these twenty years expanding the chapters on magic squares and on mathematical fallacies.
- Due to his expansive knowledge of the background literature, gained through investigating very old sources and picking out the fundamental mathematics from these works, Ahrens was also asked to write an article about mathematical games for Felix Klein's encyclopaedia Enzyklopädie der Mathematischen Wissenschaften Ⓣ(Encyclopedia of Mathematical Sciences); he contributed the 14-page article Mathematische Spiele which was published in 1902.
- Another interesting work by Ahrens is a valuable collection of quotes about mathematics and mathematicians Scherz und Ernst in der Mathematik, geflügelte und ungeflügelte Worte Ⓣ(Fun and seriousness in mathematics, well-known and less well-known words), published in 1904.
- Ahrens has understood, just to select those utterances of an author, which are characteristic of his position, his mindset, and his individuality.
- Ahrens heavily annotated the work, published in 1907, in order to make the correspondence accessible for readers of his day.
- In 1908, Ahrens, in collaboration with Paul Stäckel, published Briefwechsel zwischen C G J Jacobi und P H von Fuss über die Herausgabe der Werke Leonhard Eulers Ⓣ(Correspondence between C G J Jacobi and P H von Fuss on the publication of the works Leonhard Euler), making available letters between Carl Jacobi and Nicolaus Fuss concerning the publication of Leonard Euler's complete works.
- Euler was born in 1707 and the work by Ahrens and Stäckel was associated with the bicentennial of his birth.
- Following critical investigation of old sources, Ahrens wrote Mathematiker-Anekdoten Ⓣ(Mathematicians' Anecdotes) (1916) which is of particular interest for the study of mathematical history.
- Emil Lampe (1840-1918) writes in a review that Ahrens, as the author of Scherz und Ernst in der Mathematik, is able to select well chosen material from the wealth of its treasures about a number of mathematicians.
- In addition to these books, let us give some indication of papers that Ahrens wrote.
- By all accounts Ahrens had an amiable nature and was a loyal friend.

Born 3 March 1872, Lübz an der Elde, Mecklenburg, Germany. Died 23 April 1927, Rostock, Germany.

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Origin Germany

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive