How many possible sudoku puzzles are there In the lottery, what is the chance that two winning balls have consecutive numbers Who invented Pascal's triangle it was not Pascal pCombinatorics, the branch of mathematics concerned with selecting, arranging, and listing or counting collections of objects, works to answer all these questions. Dating back some 3000 years, and initially consisting mainly of the study of permutations and combinations, its scope has broadened to include topics such as graph theory, partitions of numbers, block designs, design of codes, and latin squares. In this emVery Short Introductionem Robin Wilson gives an overview of the field and its applications in mathematics and computer theory, considering problems from the shortest routes covering certain stops to the minimum number of colours needed to colour a map with different colours for neighbouring countries.brstrongstrong ABOUT THE SERIES The em Very Short Introductionsem series from Oxford University Press c