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A116956
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Number of functions f:{1,2,...,n}->{1,2,...,n} with odd cycles only.
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1
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1, 1, 3, 18, 157, 1800, 25551, 432376, 8494809, 190029888, 4768313275, 132626098176, 4049755214517, 134677876657792, 4845193429684167, 187490897290080000, 7765153170076158001, 342721890859339812864
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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FORMULA
| E.g.f.: sqrt((1-LambertW(-x))/(1+LambertW(-x))).
Sum_{k=0..n} binomial(n,k)*a(k)*a(n-k) = 2*n^n, n>0. - Vladeta Jovovic (vladeta(AT)eunet.rs), Oct 11 2007
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MATHEMATICA
| t = Sum[n^(n - 1) x^n/n!, {n, 1, 20}]; Range[0, 20]! CoefficientList[
Series[((1 + t)/(1 - t))^(1/2), {x, 0, 20}], x] (* Geoffrey Critzer, Dec 07 2011 *)
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CROSSREFS
| Cf. A070896, A060281, A060435, A070896.
Sequence in context: A138274 A181374 A060913 * A166887 A075678 A089901
Adjacent sequences: A116953 A116954 A116955 * A116957 A116958 A116959
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KEYWORD
| easy,nonn
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AUTHOR
| Vladeta Jovovic (vladeta(AT)eunet.rs), Mar 30 2006
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