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A060307
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Number of degree-4n permutations without odd cycles and such that number of cycles of size 2k is even (or zero) for every k.
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3
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OFFSET
| 0,2
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FORMULA
| E.g.f.: Product_{k >= 1} cosh x^(2k)/(2k).
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MATHEMATICA
| nn = 40; Select[Range[0, nn]! CoefficientList[Series[Product[Cosh[x^(2 i)/(2 i)], {i, 1, nn}], {x, 0, nn}], x], # > 0 &] (* Geoffrey Critzer, Jan 16 2012 *)
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CROSSREFS
| Cf. A003483.
Cf. A013302.
Sequence in context: A174826 A122389 A036066 * A119111 A118050 A116994
Adjacent sequences: A060304 A060305 A060306 * A060308 A060309 A060310
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KEYWORD
| easy,nonn
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AUTHOR
| Vladeta Jovovic (vladeta(AT)eunet.rs), Mar 28 2001, Aug 10 2007
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