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Search: id:A130644
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| A130644 |
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Number of degree-2n permutations without odd cycles and such that number of cycles of size 2k is odd (or zero) for every k. |
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+0
1
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| 1, 1, 6, 225, 8400, 760725, 91725480, 15563633085, 3381661483200, 1015992072520425, 360153767651277600, 160068908768727783825, 84298688029883001074400, 53051020433282263735468125
(list; graph; listen)
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OFFSET
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0,3
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FORMULA
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E.g.f.: Product_{k>0} (1+sinh(x^(2*k)/(2*k))).
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EXAMPLE
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a(2)=6 because we have (1234),(1243),(1324),(1342),(1423), and (1432).
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MAPLE
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g:=product(1+sinh(x^(2*k)/(2*k)), k=1..50): gser:=series(g, x=0, 44): seq(factorial(2*n)*coeff(gser, x, 2*n), n=0..14); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 24 2007
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CROSSREFS
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Cf. A060307.
Adjacent sequences: A130641 A130642 A130643 this_sequence A130645 A130646 A130647
Sequence in context: A061610 A054324 A117255 this_sequence A084070 A117064 A112001
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KEYWORD
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easy,nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)Eunet.yu), Aug 11 2007
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 24 2007
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