Top network posts

• 35 Penrose's remark on impossible figures
• 35 How find this $\sum_{n=1}^{\infty}\frac{H^3_{n}}{n+1}(-1)^{n+1}$
• 34 Why Cohomology Groups?
• 21 How find the sum $\sum_{n=1}^{\infty}\frac{\binom{4n-4}{n-1}}{2^{4n-3}(3n-2)}$
• 19 Which groups act freely on $S^n$?
• 19 If $f:S^1\to S^1$ doesn't have any fixed point then it is homotopic to the identity
• 16 Is there an orientable closed compact $3$-manifold such that its fundamntal group is $\mathbb{Z}$?
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