the (n − 1)st Catalan number. Therefore, pn = cn−1. See also Algebraic combinatorics Asymptotic combinatorics Burnside's lemma Combinatorial explosion Combinatorial game theory Combinatorial principles Combinatorial species Inclusion–exclusion principle Method of distinguished element Pólya enumeration theorem Sieve theory References Zeilberger, Doron, Enumerative and Algebraic Combinatorics Björner, Anders and Stanley, Richard P., A Combinatorial Miscellany Graham, Ronald L., Grötschel M., and Lovász, László, eds. (1996). Handbook of Combinatorics, Volumes 1 and 2. Elsevier (North-Holland), Amsterdam, and MIT Press, Cambridge, Mass. . Loehr, Nicholas A. (2011). Bijective Combinatorics. CRC Press. , . Stanley, Richard P. (1997, 1999). Enumerative Combinatorics, Volumes 1 and 2. Cambridge University Press. , . Goulden, Ian P. and Jackson, David M. (2004). Combinatorial Enumeration. Dover Publications. . Riordan, John (1958). An Introduction to Combinatorial Analysis, Wiley & Sons, New York (republished). Riordan, John (1968). Combinatorial Identities, Wiley & Sons, New York (republished).