Herbert Saul Wilf, 80, an innovative mathematics researcher, teacher, writer, journal editor and the University of Pennsylvania Thomas A. Scott Emeritus Professor of Mathematics, died Jan. 7 in Wynnewood.

Wilf was the author of six books and more than 160 research articles. From the 1950s, he was a pioneer in the mathematical programming of early computers, beginning with his work at Nuclear Development Associates, which led to his book *Mathematical Methods for Digital Computers*, written with A. Ralston.

From 1959 to 1962, he taught at the University of Illinois. His early work focused on numerical analysis and complex analysis, and led to numerous research papers as well as a textbook, *Mathematics for the Physical Sciences*.

Wilf taught at the University of Pennsylvania from 1962 until his retirement in 2008. In 1973, he received the University of Pennsylvania's Christian and Mary Lindback Award for excellence of undergraduate teaching. In 1996, he received the Deborah and Franklin Tepper Haimo Award for distinguished teaching of mathematics, from the Mathematical Association of America.

In the 1960s, Wilf became interested in the newly developing field of combinatorial analysis. He wrote fundamental research papers, forming the foundation of today's work in discrete mathematics with its applications to computer algorithms and its close interconnections with the mathematical fields of algebra and probability theory.

He did pathbreaking work with D. Zeilberger of Rutgers University on a theory of computerized proofs for combinatorial identities. For this work, they were awarded the Leroy P. Steele Prize of the American Mathematical Society for Seminal Contributions to Research in 1998.

Overall, he contributed more than 135 papers in combinatorics and wrote four influential books, including *generating functionology* and *A = B*, the latter with M. Petkovsek and D. Zeilberger. In 2004, he was awarded the Euler Medal for Lifetime Contributions by the Institute for Combinatorics and its Applications. He supervised 26 Ph.D. students in combinatorics at the University of Pennsylvania.

Wilf was a pioneer advocate of the open electronic publishing of books and journals. Many of his books are available for free downloads on his web page, **www.math.upenn.edu/~wilf [1]**, which registered 350,000 downloads last year. He co-founded two major journals, *The Journal of Algorithms* in 1980 with D. Knuth, and *The Electronic Journal of Combinatorics*in 1994 with N. Calkin.

From 1987 to 1992, he also served as editor-in-chief of *The American Mathematical Monthly*, a leading journal that aims for expository and readable dissemination of mathematical work for teachers and researchers. Wilf spoke at colleges, universities and mathematics conferences throughout the world.

Wilf co-authored research papers with more than 60 mathematicians. His final papers were as influential as his early ones, including "There's Plenty of Time for Evolution" with W. Ewens, which appeared in the Proceedings of the National Academy of Sciences in 2010.

Born in 1931 in Philadelphia, Wilf earned a B.S. in mathematics from the Massachusetts Institute of Technology in 1952, and a Ph.D. in mathematics from Columbia University in 1958.

Wilf is survived by his wife of 59 years, Ruth Tumen Wilf; daughter Susan Wilf; sons David Wilf and Peter Wilf; and six grandchildren.

Donations to establish an award recognizing outstanding student achievement can be sent to: the Herbert S. Wilf Award Fund, Department of Mathematics, University of Pennsylvania, 209 S. 33rd St., Philadelphia, PA 19104-6395.