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 Constituent
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Apr
19
answered Approach to determining if a graph is planar by inspection/kuratowski's theorem
Apr
15
comment Simple maths and a typo: impossible answer?
There are also solutions with $y=18$ and $y=-19$ since we then have $(2a-1)^2=13^2$ and we can have $a=7$ or $a=-6$.
Feb
16
answered Prove if r is the smallest positive integer such that all entries of at least one row of Sr are positive, then rad(G) = r.
Jan
29
answered Find all natural numbers for which $3\binom{2n}{n+1}=2\binom{2n+1}{n-1}$ holds true
Jan
26
revised Rank in row echelon form
1-cd not -cd+1
Jan
26
revised Rank in row echelon form
added 35 characters in body
Jan
26
answered Rank in row echelon form
Dec
20
awarded  Constituent
Dec
9
awarded  Caucus
Dec
4
comment Question on Graphs?
Note that when using open neighbourhoods of vertex sets it can be awkward to have some elements of $A$ in $N(A)$ and some not in $N(A)$ as can happen with this definition. I prefer to use a definition in terms of closed neighbourhoods as follows: $N(A) := (\bigcup_{v\in A} N[v] ) \setminus A$, where $N[v]:=\{v\} \cup N(v)$.
Oct
17
answered Maple not displaying graph
Sep
8
answered Smallest non-hamiltonian k-connected graph
Aug
6
comment How many distinct chromatic polynomials are there for simple connected graphs?
so are you looking for the numbers of different chromatic polynomials or the numbers of graphs with unique chromatic polynomials?
Aug
6
comment How many distinct chromatic polynomials are there for simple connected graphs?
@Jernej I thought your answer was useful and may even be what Hooked was looking for, hopefully we will find out!
Aug
5
comment How many distinct chromatic polynomials are there for simple connected graphs?
I have verified the above numbers for general graphs up to 8 vertices and for connected graphs the sequence of chromatically unique graphs is 1, 1, 2, 4, 10, 27, 100, 570.
Aug
5
comment How many distinct chromatic polynomials are there for simple connected graphs?
The definition given at mathworld.wolfram.com/ChromaticallyUniqueGraph.html is that this sequence lists the number of graphs which have a unique polynomial, not the number of different polynomials...
Jul
8
comment Software to find out adjacency matrix of a graph.
There are shortcuts using the underlined letters, so alt V to get to the vertex menu, etc. I've never needed edge colouring, so didn't implement it, sorry. It should be possible to add it with a bit of coding knowledge though.
Jul
8
comment Software to find out adjacency matrix of a graph.
Sorry, no manual, but if there's something that doesn't do what you think, feel free to ask here.
Jul
5
awarded  Yearling
Jun
20
revised The number of dominating sets of a bipartite graph is not exactly divisible by $2$
Tidied up the flow