Abstract
It is shown that there are (2n-r-1 n-r) noncrossing partitions of an n-set together with a distinguished block of size r, and ( nk-1)(n-r-1k-2) of these have k blocks, generalizing a result of Bóna on partitions with one crossing. Furthermore, specializing natural q-analogues of these formulae with q equal to certain dth roots-of-unity gives the number of such objects having d-fold rotational symmetry.
Original language | English (US) |
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Pages (from-to) | 83-87 |
Number of pages | 5 |
Journal | Ars Combinatoria |
Volume | 99 |
State | Published - Apr 2011 |
Keywords
- Cyclic sieving phenonomenon
- Noncrossing partition