# Combinatorial Mathematics - Fall 2008 Typos

This page lists the typographical errors that have been discovered in the Fall 2008 pre-publication version of Combinatorial Mathematics, by Douglas B. West. This page is of interest only to those persons having a copy of this draft, particularly the students in my course, other users of the text, and reviewers. Please send comments and corrections on the book to west @ math.uiuc.edu. Contributors are noted in parentheses. Please do not send comments about incorrect page numbers in the index (and note that all page numbers there are odd for \TeX nical reasons); however, I do want to know of missing terms that should be added to the index.

## Category 1: Mathematical typos/corrections to text

• p39, Exercise 1.2.20: the upper limit of the first sum should be m (Farzad Hassanzadeh)
• p51, Theorem 1.3.16: A closing "}" is missing in the definition of L.
• p117, Example 3.1.11: Before the last display, there should be no parentheses on 1-x in the numerator (Mu Sun)
• p123, Theorem 3.1.23: In the proof, the upper part of the last binomial coefficient should be x-k+n.
• p137, Example 3.2.19: The exponent [n] should be (n) (Farzad Hassanzadeh)
• p201, Example 4.1.26: This example is about partitioning n, but it is stated as partitioning [n] throughout the example. (Farzad Hassanzadeh)
• p354, after Definition 7.1.5: The second "Hk,n-1" should be "Hk,n" (Dan Schreiber)
• p414, Exercise 8.1.9 includes Exercise 8.1.6
• p419, Remark 8.2.3 & Prop 8.2.4: The inverted "!" should be "<"
• p421, Proposition 8.2.8: "earlier numbers" should be "earlier neighbors, and "was not been" should be "has not been" (Farzad Hassanzadeh)
• p430, Exercise 8.2.8: part (a) is the converse of Theorem 8.2.13 (Farzad Hassanzadeh)
• p484, Exercise 9.2.12: "H" should be "C", and the definition of "fragment" should be included
• .
• p542, Theorem 10.2.11: "at most R(p-1,q) neighbors and at most R(p,q-1) nonneighbors" should be "at most R(p-1,q)-1 neighbors and at most R(p,q-1)-1 nonneighbors" (Farzad Hassanzadeh)
• p637, Remark 12.1.3: "Since order relations are symmetric" should be "Since order relations are reflexive"
• p762, Proposition 14.1.5: In both inequalities, equality holds for x=0. (Farzad Hassanzadeh)
• p801, before Theorem 14.3.18: trees are balanced, but forests need not be
• (Kyle Fox?)
• p803, Remark 14.3.19: When the indicator variables are independent, E() does not simplify to E(X)²; it simplifies to E(X)²+∑iP(X=1)P(X=0). (Farzad Hassanzadeh)

## Category 2: Comments, clarifications, and cross-references

• p640, Example 12.1.11: The posets with cover graph C6 are no longer in Example 12.1.5
• p643, before Theorem 12.1.8: The reference to Chapter 19 is wrong; network flow is no longer there. Elementary aspects of network flow are moving to the section on Menger's Theorem.

## Category 3: Minor typos and corrections

Note: Corrections involving addition, deletion, or alteration of one punctuation mark may be implemented without being listed here. Corrections to capitalization may also be omitted.
• p54, before Example 1.3.22: "binary tree" should be "binary trees" (Dan Schreiber)
• p122, after Example 3.1.22: "are of so" should be "are so"