Formal proof that a complete graph $K_n$ is Class 1 if n is even and it is Class 2 if n is odd.
12557
Coloring Graph Problem
157939
prove that a graph is one-ended
158856
Prove that a graph with the same number of edges and vertices contains one cycle
20544
Proving that if $G$ has a Hamiltonian circuit, then the line graph $L(G)$ also has a Hamiltonian Circuit
84010
Combinatorial proof that $\sum \limits_{k=0}^n \binom{2k}{k} \binom{2n-2k}{n-k} (-1)^k = 2^n \binom{n}{n/2}$ when $n$ is even
129680
Prove that $n$ is even.
128834
Proving the number of even and odd permutations of a subgroup $H<S_{n}$ are equal, provided $H$ is not contained in $A_{n}$
106801
Labelled spanning trees of $K_n-e$
59831
How to relate combinatorial proof to bipartite graphs?
146933
Proving bipartition in a connected planar graph
61340
Prove that there exists bipartite graph with this degree sequence: $(3,3,3,3,3,5,6,6,6,6,6,6,6,6)$
127843
Prove that, for any natural number $k$ $\exists m \in M $ s.t i) $m$ has exactly $k$ $1$'s, an
48692
A problem about the graph theory
113015
Eulerian Paths in a Complete Graph $K_5$
147282
Prove that in every graph with at least two vertices, there are at least two vertices which have the same degree?
114796
Direct proof that the product of odd integers is odd
92057
Prove that for every odd integer n, there is a group...