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A103620
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Number of permutations of n elements admitting a fourth root.
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2
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1, 1, 1, 3, 9, 45, 225, 1575, 11130, 100170, 897750, 9875250, 108523800, 1410809400, 18332414100, 274986211500, 4127136413400, 70161319027800, 1192076391706200, 22649451442417800, 430247983427262000, 9035207651972502000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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LINKS
| H. S. Wilf, Generatingfunctionology, 2nd edn., Academic Press, NY, 1994, p. 149, Eq. 4.8.2.
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FORMULA
| E.g.f.: ((1+x)/(1-x))^(1/2)*Product(1/2*cos(1/2*x^(2*m)/m)+1/2*cosh(1/2*x^(2*m)/m), m = 1 .. infinity).
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CROSSREFS
| Cf. A003483, A103619, A102687.
Sequence in context: A068100 A012821 A000246 * A138315 A038059 A174318
Adjacent sequences: A103617 A103618 A103619 * A103621 A103622 A103623
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KEYWORD
| nonn
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AUTHOR
| Vladeta Jovovic (vladeta(AT)eunet.rs), Feb 11 2005
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