16,609 reputation
21866
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location Mexico City
age
visits member for 2 years, 6 months
seen 7 mins ago

Hello, I am a freshman at The National Autonomous University of Mexico (UNAM).

My interests are contest problems,elementary number theory, combinatorics, graph theory, linear algebra, group theory, abstract algebra and I have been meaning to learn category theory and matroids.


18h
comment $x^2-y^2=2s$, s cannot be an odd integer
Oh, this solution is much better than mine. +1
18h
answered $x^2-y^2=2s$, s cannot be an odd integer
18h
revised $x^2-y^2=2s$, s cannot be an odd integer
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18h
comment Triangle-free graph with 5 vertices
with $5$ vertices. If there is no restiction on the number of vertices you can find a bipartite graph with as many edges as desired.
18h
comment Triangle-free graph with 5 vertices
Oh, we thought of the same thing, they say poor minds think alike.
18h
answered Triangle-free graph with 5 vertices
22h
revised Number of ways to arrange items
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22h
comment Number of ways to arrange items
$f_k(n)$ are the same as the stirling numbers of the first kind
22h
revised Number of ways to arrange items
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23h
revised Number of ways to arrange items
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23h
revised Number of ways to arrange items
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23h
answered Intersect of Stabilizers is a Normal Group
23h
answered Number of ways to arrange items
1d
awarded  Custodian
1d
comment Minimize total cost of one kilometer
Something is wrong, the cost per hour should always be over $100$. are you sure the cost per hour is $25$ when the speed is $25$?
1d
answered Set with distinct subset sums
1d
comment How to solve this kind of problem?
I solved it using integers, I think it becomes harder if we can only use naturals.
1d
revised How to solve this kind of problem?
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1d
comment Check if Sequence is Graphic: 8, 8, 7, 7, 6, 6, 4, 3, 2, 1, 1, 1
I mean, you should count the degrees in the graph to make sure, but I can't find more conclusive evidence it is graphic
1d
comment Check if Sequence is Graphic: 8, 8, 7, 7, 6, 6, 4, 3, 2, 1, 1, 1
Well, I counted the degrees in the graph in the solution and it is correct, are you sure you copied the sequence correctly?