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Search: id:A051685
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| A051685 |
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Auxiliary sequence for calculation of number of even permutations of degree n and order exactly 4. |
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+0
3
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| 0, 0, 0, -6, -30, 0, 420, 2100, 6804, -20160, -376200, -2102760, -6606600, 53237184, 965306160, 5941244400, 12774059760, -305998041600, -5264368533216, -33983490935520, -16008359119200, 3139364813249280, 52132631033313600, 341037535726730304, -715693892444414400
(list; graph; listen)
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OFFSET
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1,4
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REFERENCES
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V. Jovovic, Some combinatorial characteristics of symmetric and alternating groups (in Russian), Belgrade, 1980, unpublished.
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FORMULA
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a(n) = c(n, 4), where c(n, d)=Sum_{k=1..n} (-1)^(k+1)*(n-1)!/(n-k)! *Sum_{l:lcm{k, l}=d} c(n-k, l), c(0, 1)=1.
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CROSSREFS
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Cf. A001189, A001473, A051684.
Sequence in context: A054748 A143563 A122802 this_sequence A165734 A123624 A066197
Adjacent sequences: A051682 A051683 A051684 this_sequence A051686 A051687 A051688
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KEYWORD
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easy,sign
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AUTHOR
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Vladeta Jovovic (vladeta(AT)eunet.rs)
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EXTENSIONS
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More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 05 2003
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