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Search: id:A091441
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| A091441 |
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Table (by antidiagonals) of permutations of two types of objects so that each cycle contains at least one object of each type. Each type of object labeled from its own label set. |
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1
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| 1, 2, 2, 6, 8, 6, 24, 36, 36, 24, 120, 192, 216, 192, 120, 720, 1200, 1440, 1440, 1200, 720, 5040, 8640, 10800, 11520, 10800, 8640, 5040, 40320, 70560, 90720, 100800, 100800, 90720, 70560, 40320, 362880, 645120, 846720, 967680, 1008000, 967680
(list; table; graph; listen)
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OFFSET
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1,2
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REFERENCES
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F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like Structures, Cambridge, 1998, pg 114 (2.4.42)
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FORMULA
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Double e.g.f.: A(x, y) = Sum_{i, j>=0} (x^i*y^j/(i!*j!)) = (1-x)*(1-y)/(1-x-y).
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EXAMPLE
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1 2 6 24 120 ...
2 8 36 192 1200 ...
6 36 216 1440 10800 ...
24 192 1440 11520 100800 ...
120 1200 10800 100800 1008000 ...
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CROSSREFS
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Sequence in context: A092522 A116542 A142243 this_sequence A099490 A033724 A033748
Adjacent sequences: A091438 A091439 A091440 this_sequence A091442 A091443 A091444
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KEYWORD
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nonn,tabl
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AUTHOR
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Christian G. Bower (bowerc(AT)usa.net), Jan 09 2004
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