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Search: id:A102687
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| A102687 |
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Number of different squares of mappings of a finite set of n elements into itself. |
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+0
13
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| 1, 3, 12, 100, 1075, 13356, 197764, 3403576, 66159405
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OFFSET
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1,2
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COMMENT
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Let A be a finite set of cardinal n, F be the set of mappings from A to A and F_2 be the subset of F including all g such that there exists f in F with g = fof (composition of f with itself). Then a(n) = #F_2.
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CROSSREFS
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Cf. A102709.
Sequence in context: A162055 A067300 A133359 this_sequence A141535 A111485 A080447
Adjacent sequences: A102684 A102685 A102686 this_sequence A102688 A102689 A102690
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KEYWORD
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nonn,more
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AUTHOR
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Eric Wegrzynowski (Eric.Wegrzynowski(AT)lifl.fr), Feb 03 2005
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EXTENSIONS
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a(7) from Vladeta Jovovic (vladeta(AT)eunet.rs), Feb 05 2005
a(8) and a(9) from Joshua Zucker (joshua.zucker(AT)stanfordalumni.org), May 18 2006
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