User contributions for 652024330006

22 May 2026

• 14:5614:56, 22 May 2026 diff hist +200 组合数学 (Spring 2026) →Announcement
• 14:5514:55, 22 May 2026 diff hist +61 组合数学 (Spring 2026) →Assignments
• 14:5414:54, 22 May 2026 diff hist −1 组合数学 (Spring 2026)/Problem Set 3 →Problem 4 current
• 14:5414:54, 22 May 2026 diff hist +6 组合数学 (Spring 2026)/Problem Set 3 No edit summary
• 14:4614:46, 22 May 2026 diff hist +18 组合数学 (Spring 2026)/Problem Set 3 →Problem 4
• 14:2114:21, 22 May 2026 diff hist +31 组合数学 (Spring 2026)/Problem Set 3 →Problem 5
• 14:1814:18, 22 May 2026 diff hist −2 组合数学 (Spring 2026)/Problem Set 3 →Problem 4
• 14:1714:17, 22 May 2026 diff hist −1 组合数学 (Spring 2026)/Problem Set 3 →Problem 3
• 14:1614:16, 22 May 2026 diff hist −5 组合数学 (Spring 2026)/Problem Set 3 →Problem 1
• 13:4913:49, 22 May 2026 diff hist 0 组合数学 (Spring 2026)/Problem Set 3 No edit summary
• 13:3113:31, 22 May 2026 diff hist +2,749 N 组合数学 (Spring 2026)/Problem Set 3 Created page with "==Problem 1== We color each non-empty subset of <math>[n]=\{1,2,\ldots,n\}</math> with one of the <math>r</math> colors in <math>[r]</math>. Show that for any finite <math>r</math> there is a finite <math>N</math> such that for all <math>n\ge N</math>, for any <math>r</math>-coloring of non-empty subsets of <math>[n]</math>, there always exist <math>1\le i<j<k\le n</math> such that the intervals <math>[i,j)=\{i,i+1,\ldots, j-1\}</math>, <math>[j,k)=\{j,j+1,\ldots, k-1\}<..." Tag: Visual edit: Switched

21 April 2026

• 12:2612:26, 21 April 2026 diff hist +200 组合数学 (Spring 2026) →Announcement
• 12:2512:25, 21 April 2026 diff hist +61 组合数学 (Spring 2026) →Assignments
• 11:5511:55, 21 April 2026 diff hist 0 组合数学 (Spring 2026)/Problem Set 2 →Problem 4 current
• 11:1011:10, 21 April 2026 diff hist +10 组合数学 (Spring 2026)/Problem Set 2 →Problem 4
• 11:0911:09, 21 April 2026 diff hist −8 组合数学 (Spring 2026)/Problem Set 2 →Problem 6
• 11:0811:08, 21 April 2026 diff hist +12 组合数学 (Spring 2026)/Problem Set 2 →Problem 3
• 11:0811:08, 21 April 2026 diff hist +35 组合数学 (Spring 2026)/Problem Set 2 →Problem 2
• 11:0711:07, 21 April 2026 diff hist −3 组合数学 (Spring 2026)/Problem Set 2 →Problem 1
• 11:0611:06, 21 April 2026 diff hist +7 组合数学 (Spring 2026)/Problem Set 2 →Problem 6
• 10:5710:57, 21 April 2026 diff hist 0 组合数学 (Spring 2026)/Problem Set 2 →Problem 4
• 10:5610:56, 21 April 2026 diff hist +2 组合数学 (Spring 2026)/Problem Set 2 →Problem 6
• 10:5210:52, 21 April 2026 diff hist +3,480 N 组合数学 (Spring 2026)/Problem Set 2 Created page with "== Problem 1 == Suppose <math> n \geq 4 </math>, and let <math> H </math> be an <math>n</math>-uniform hypergraph with at most <math> \frac{4^{n−1}}{3^n} </math> (hyper)edges. Prove that there is a coloring of the vertices of <math> H </math> by four colors so that in every (hyper)edge all four colors are represented. == Problem 2 == Use the Lovász Local Lemma to show that, if <math> 4\binom{k}{2}\binom{n}{k-2}2^{1-\binom{k}{2}} \leq 1 </math>, then it is possibl..."

7 April 2026

• 08:1008:10, 7 April 2026 diff hist +8 m 组合数学 (Spring 2026)/Problem Set 1 →Problem 5 current Tag: Visual edit

25 March 2026

• 06:1006:10, 25 March 2026 diff hist 0 组合数学 (Spring 2026) →Announcement Tag: Visual edit: Switched
• 06:0906:09, 25 March 2026 diff hist +194 组合数学 (Spring 2026) →Announcement Tag: Visual edit: Switched

24 March 2026

• 13:5113:51, 24 March 2026 diff hist +93 组合数学 (Spring 2026) No edit summary
• 13:4913:49, 24 March 2026 diff hist +55 组合数学 (Spring 2026) →Assignments Tag: Visual edit: Switched
• 13:3113:31, 24 March 2026 diff hist +2,329 N 组合数学 (Spring 2026)/Problem Set 1 Created page with "== Problem 1 == Fix positive integers <math>n</math> and <math>k</math>. Let <math>S</math> be a set with <math>|S|=n</math>. Find the numbers of <math>k</math>-tuples <math>(T_1,T_2,\dots,T_k)</math> of subsets <math>T_i</math> of <math>S</math> subject to each of the following conditions separately. Briefly explain your answer. * <math>T_1\subseteq T_2\subseteq \cdots \subseteq T_k.</math> * The <math> T_i</math>s are pairwise disjoint. * <math> T_1\cup T_2\cup \cdots..."