Ira Gessel
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Registered User
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2d |
answered | The proportion between permutations and derangements. |
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Jun 10 |
accepted | The number of lattice paths below y=n/m x for gcd(m,n) = 1 |
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Jun 9 |
answered | The number of lattice paths below y=n/m x for gcd(m,n) = 1 |
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May 29 |
comment |
Symmetric powers of Schur polynomials You can use John Stembridge's SF package for Maple: dept.math.lsa.umich.edu/~jrs/maple.html |
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May 17 |
revised |
Enumerating unlabeled trees with degree at most 3 deleted 10 characters in body |
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May 17 |
answered | Enumerating unlabeled trees with degree at most 3 |
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May 13 |
comment |
Show that this ratio of factorials is always an integer It might be worth mentioning Landau's theorem, digreg.mathguide.de/cgi-bin/ssgfi/…, which gives this argument in a much more general setting. |
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May 13 |
awarded | ● Nice Answer |
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May 12 |
awarded | ● Nice Answer |
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May 12 |
answered | Show that this ratio of factorials is always an integer |
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May 6 |
comment |
Enumerating/counting paths of a given length on a 2D lattice It seems to me that this should be solvable by a straightforward application of Burnside's lemma. |
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May 6 |
answered | Hypergeometric identities |
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Apr 29 |
awarded | ● Student |
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Apr 29 |
comment |
Cayley’s Theorem regarding marked trees Unlabeled (the usual term) trees are not impossible to count. They were first counted by Cayley (before he counted labeled trees, I believe). The numbers are A000055 in the OEIS. |
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Apr 29 |
asked | Reference request: enumeration under group action |
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Apr 29 |
accepted | Sign of coefficients |
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Apr 29 |
revised |
Sign of coefficients added 136 characters in body |
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Apr 29 |
answered | Sign of coefficients |
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Mar 28 |
comment |
Maximal chain of 1s in binary strings Some relevant papers are Mark Schilling's papers on long runs, csun.edu/~hcmth031/research.html. |
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Mar 24 |
answered | Cyclically symmetric functions |
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Mar 4 |
answered | Name of certain combinatorial numbers? |
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Feb 26 |
answered | Reference request on symmetric polynomials |
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Feb 22 |
comment |
trigonometric identity needed for sums involving secants You can still try the partial fraction expansion, but it probably won't simplify as much. Is there any reason to think that there's a simple formula for this case? |
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Feb 21 |
accepted | trigonometric identity needed for sums involving secants |
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Feb 21 |
comment |
trigonometric identity needed for sums involving secants I have edited my post to include the full solution. |
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Feb 21 |
revised |
trigonometric identity needed for sums involving secants added 1804 characters in body; deleted 1 characters in body |
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Feb 21 |
answered | trigonometric identity needed for sums involving secants |
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Feb 19 |
comment |
Distribution of distances in permutations You don't include abs(3-1) because 1 and 3 are not consecutive in (1,2,3). |
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Feb 7 |
accepted | What is the cardinality of the family of unlabelled bipartite graphs on n vertices? |
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Feb 6 |
comment |
What is the cardinality of the family of unlabelled bipartite graphs on n vertices? The published version of this part of Li's thesis is I. M. Gessel and J. Li, Enumeration of point-determining graphs, J. Combinatorial Theory Ser. A 118 (2011), 691-612. But the formula we give in this paper for the cycle index series for bicolored graphs isn't really new, I don't think; certainly the formula for unlabeled bicolored graphs that you get from it isn't new (and this isn't the point of our paper). But the paper does have references to earlier work on this topic. |
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Feb 4 |
answered | What is the cardinality of the family of unlabelled bipartite graphs on n vertices? |
