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visits | member for | 3 years, 5 months |
seen | 3 hours ago | |
stats | profile views | 823 |
Apr 15 |
awarded | Informed |
Apr 14 |
revised |
Conjecture relating differential equation and sum of a function over partitions
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Apr 8 |
revised |
Erdos distance problem n=12
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Apr 6 |
awarded | Nice Answer |
Apr 3 |
awarded | Excavator |
Apr 3 |
revised |
series expansion of the q-Pochhammer symbol
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Mar 26 |
answered | Is there an interesting species whose generating function gives the zigzag numbers? |
Feb 23 |
comment |
Number of matrices with no repeated columns or rows
The problem of counting these matrices up to row and column permutations is solved in I. M. Gessel and J. Li, Enumeration of point-determining graphs, J. Combinatorial Theory Ser. A 118 (2011), 591-612, available online at arxiv.org/abs/0705.0042. (In the paper they are called "semi-point-determining bicolored graphs".) Of course, as in most unlabeled graphical enumeration problems, the formula is not simple, and might not be so helpful in deriving an asymptotic formula. The numbers in Richard's formula are sequence A181230 in the OEIS. |
Feb 8 |
answered | Exponential of a specific hypergeometric series |
Feb 5 |
answered | Exponential of a specific hypergeometric series |
Jan 3 |
comment |
A problem on counting k-subsets of {-n,-n+1,…,n-1,n} satisfying that sum of elements equal to 0
You're right. I rewrote it to use the q-binomial theorem. |
Jan 3 |
revised |
A problem on counting k-subsets of {-n,-n+1,…,n-1,n} satisfying that sum of elements equal to 0
added 174 characters in body |
Jan 3 |
comment |
A problem on counting k-subsets of {-n,-n+1,…,n-1,n} satisfying that sum of elements equal to 0
I have rewritten my answer to make this clearer. |
Jan 3 |
revised |
A problem on counting k-subsets of {-n,-n+1,…,n-1,n} satisfying that sum of elements equal to 0
deleted 4 characters in body |
Jan 3 |
answered | A problem on counting k-subsets of {-n,-n+1,…,n-1,n} satisfying that sum of elements equal to 0 |
Dec 27 |
comment |
Asymptotic growth for $\sum_{i=1}^{n-1}(n-i)\binom{k}{i}$
For $n>k$ the sum is equal to $(2^k-1)n -2^{k-1}k$ (by the binomial theorem) so Mathematica's asymptotic expansion isn't very helpful. |
Dec 13 |
comment |
Quadratic transformation of hypergeometric function 2F1
It seems unlikely, but it would be difficult to prove that there is no such transformation. |
Dec 10 |
comment |
Counting regular Hypergraphs
You can consider the problem of counting hypergraphs on n vertices with specified degrees of the vertices as counting partitions of a multiset in which each block is a set. Some references for this problem can be found in my paper Symmetric Functions and P-Recursiveness, J. Combin. Theory Ser. A 53 (1990), 257–285, people.brandeis.edu/~gessel/homepage/papers/dfin.pdf |
Nov 27 |
awarded | Nice Answer |
Nov 27 |
comment |
Combinatorial identities
Very nice proof! |