...1, Cambridge University Press, Cambridge 1915 (Reprinted: Chelsea, New York, 1960). 6. J. Riordan, An Introduction to Combinatorial Analysis, John Wiley and Sons, New York, 1958. 7. GC Rota, The number of partitions of a set, Amer. Math. Monthly, 71 (1964), 498-504. THE PENNSYLVANIA...