User Grigory M

4 votes

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Relationship between degrees of continued fractions

answered Jun 24, 2011 at 19:47

4 votes

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Moves for regular homotopies of immersions of $S^1$ in the plane

answered Dec 13, 2013 at 20:19

4 votes

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Relationship between topological and Quillen's K-theory

answered Dec 17, 2013 at 21:21

4 votes

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Prove that $PSL(2,9)\cong A_6.$

answered Nov 26, 2013 at 15:11

4 votes

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Unit or non-zero octonions form an $A_\infty$-space?

answered May 15, 2014 at 20:27

4 votes

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Is this morphism of spectra zero in the stable homotopy category?

answered Jan 8, 2015 at 20:20

4 votes

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Finite summation with binomial coefficients, $\sum (-1)^k\binom{r}{k} \binom{k/2}{q}$

answered Jan 10, 2015 at 20:45

4 votes

Combinatorial interpretation of identity: $\sum\limits_{j=0}^b\binom{b}{j}^2\binom{n+j}{2b}=\binom{n}{b}^2$

answered Jun 20, 2015 at 20:02

4 votes

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When do 10 points lie on a cubic? (a la Pascal)

answered Oct 19, 2017 at 18:41

4 votes

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Uniqueness of submanifold representing second cohomology class

answered Nov 10, 2017 at 16:20

4 votes

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Weird Combinatorial Identity: $n = \frac{n+1}{n^n - 1} \sum_{k=1}^{n/2} \binom{n-k}{k-1} n^k (n - 1)^{n+1-2k}$

answered Nov 7, 2017 at 23:33

3 votes

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Explicit formula for Higher Bockstein

answered Nov 24, 2017 at 11:44

3 votes

Binomial Sum Related to Fibonacci: $\sum\binom{n-i}j\binom{n-j}i=F_{2n+1}$

answered Dec 31, 2014 at 15:36

3 votes

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Hopf invariant and the linking number

answered Dec 5, 2013 at 13:20

3 votes

Cup Product Structure on the Projective Space

answered Dec 30, 2013 at 8:32

3 votes

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Converse of a fixed-point theorem

answered Apr 30, 2014 at 23:37

3 votes

How prove this $\sum_{k=0}^n \binom{n}{k} \binom{(p-1)n}{k} \binom{pn+k}{k} = \binom{pn}{n}^2 $

answered Feb 2, 2014 at 21:47

3 votes

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A (somewhat) conceptual proof that the boundary of a fundamental class of a manifold with boundary goes to a fundamental class?

answered Jan 11, 2014 at 17:40

3 votes

An example where $\frac{(2m)!(2n)!}{m!n!(m + n)!}$ is the number of ways of counting something?

answered Dec 21, 2014 at 11:12

3 votes

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What motiveted Gauss to formulate his theorem on quadratic reprocity?

answered Dec 20, 2014 at 12:21

3 votes

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Excision via simplicial sets

answered Jun 15, 2011 at 6:13

3 votes

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Why is this isomorphic to the reduced homology group?

answered May 29, 2011 at 14:54

3 votes

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equivalent definitions of orientation

answered Jun 7, 2011 at 20:32

3 votes

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Minimal number of contractible sets covering $\mathbb{CP}^3$

answered Jun 8, 2011 at 18:30

3 votes

A homotopy equivalence between spaces $B\Gamma$ and $K\Gamma$ for a graph of groups on a graph $\Gamma$

answered Jun 19, 2011 at 19:45

3 votes

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Quaternionic veronese Embedding

answered Apr 8, 2011 at 15:04

3 votes

$K(\mathbb R P^n)$ from $K(\mathbb C P^k)$

answered Apr 1, 2011 at 19:12

3 votes

Does a map of spaces inducing an isomorphism on homology induce an isomorphism between the homologies of the loop spaces?

answered Apr 5, 2011 at 17:47

3 votes

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Counting subsets with r mod 5 elements

answered Aug 6, 2010 at 19:09

3 votes

Not quite Fermat's Last Theorem

answered Aug 2, 2010 at 13:08

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207 Answers

Relationship between degrees of continued fractions

Moves for regular homotopies of immersions of $S^1$ in the plane

Relationship between topological and Quillen's K-theory

Prove that $PSL(2,9)\cong A_6.$

Unit or non-zero octonions form an $A_\infty$-space?

Is this morphism of spectra zero in the stable homotopy category?

Finite summation with binomial coefficients, $\sum (-1)^k\binom{r}{k} \binom{k/2}{q}$

Combinatorial interpretation of identity: $\sum\limits_{j=0}^b\binom{b}{j}^2\binom{n+j}{2b}=\binom{n}{b}^2$

When do 10 points lie on a cubic? (a la Pascal)

Uniqueness of submanifold representing second cohomology class

Weird Combinatorial Identity: $n = \frac{n+1}{n^n - 1} \sum_{k=1}^{n/2} \binom{n-k}{k-1} n^k (n - 1)^{n+1-2k}$

Explicit formula for Higher Bockstein

Binomial Sum Related to Fibonacci: $\sum\binom{n-i}j\binom{n-j}i=F_{2n+1}$

Hopf invariant and the linking number

Cup Product Structure on the Projective Space

Converse of a fixed-point theorem

How prove this $\sum_{k=0}^n \binom{n}{k} \binom{(p-1)n}{k} \binom{pn+k}{k} = \binom{pn}{n}^2 $

A (somewhat) conceptual proof that the boundary of a fundamental class of a manifold with boundary goes to a fundamental class?

An example where $\frac{(2m)!(2n)!}{m!n!(m + n)!}$ is the number of ways of counting something?

What motiveted Gauss to formulate his theorem on quadratic reprocity?

Excision via simplicial sets

Why is this isomorphic to the reduced homology group?

equivalent definitions of orientation

Minimal number of contractible sets covering $\mathbb{CP}^3$

A homotopy equivalence between spaces $B\Gamma$ and $K\Gamma$ for a graph of groups on a graph $\Gamma$

Quaternionic veronese Embedding

$K(\mathbb R P^n)$ from $K(\mathbb C P^k)$

Does a map of spaces inducing an isomorphism on homology induce an isomorphism between the homologies of the loop spaces?

Counting subsets with r mod 5 elements

Not quite Fermat's Last Theorem