Combinatorics Pigeonhole principle series
72256
Prove there exists two sub-sets of indices $I,J\subseteq [2n]$ such that $\sum_{i\in I}a_i=\sum_{j\in J}b_j$
45204
Combinatorial proofs: having a difficult time understanding how to write them out
75852
Using Pigeonhole Principle to prove two numbers in a subset of $[2n]$ divide each other
5801
Combinatorial proof help
45448
Minimum number of $k$-partitions of a set of size $n$ to enumerate all $n \choose k$ combinations
107628
Combinatorial group theory books
39724
Combinatorial Identities
152333
A problem based on pigeonhole
68882
Path to Combinatorics Problem [$1.11$]
153692
Generating and solving recurrence relations
150324
Pigeonhole principle: prove that any set of $n+1$ integers from $\{1,2,...,2n\}$ has two consecutive integers differ by one.
35648
How many permutations of the set n={1,2,3,3,3,4,4,5} are possible without any consecutive identical elements?
134440
An unexpected application of non-trivial combinatorics
13860
IMO/1981 - Combinatorics
93459
Number of permutations of unspecified length
51638
pigeonhole principle divisibility proof
97314
Counting nearly-sorted permutations