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Search: id:A103620
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| A103620 |
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Number of permutations of n elements admitting a fourth root. |
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+0
3
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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
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OFFSET
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0,4
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LINKS
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H. S. Wilf, Generatingfunctionology, 2nd edn., Academic Press, NY, 1994, p. 149, Eq. 4.8.2.
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FORMULA
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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
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Cf. A003483, A103619, A102687.
Sequence in context: A068100 A012821 A000246 this_sequence A138315 A038059 A004990
Adjacent sequences: A103617 A103618 A103619 this_sequence A103621 A103622 A103623
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KEYWORD
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nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)eunet.rs), Feb 11 2005
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