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Search: id:A005981
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| A005981 |
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2 up, 2 down, 2 up, ... permutations of length 2n+1.
(Formerly M4276)
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+0
5
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| 1, 6, 71, 1456, 45541, 2020656, 120686411, 9336345856, 908138776681, 108480272749056, 15611712012050351, 2664103110372192256, 531909061958526321421
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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P. R. Stein, personal communication.
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LINKS
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B. Shapiro and A. Vainshtein, Counting real rational functions with all real critical values, Moscow Math. J., 3 (2003), 647-659.
Eric Weisstein's World of Mathematics, Generalized Hyperbolic Functions
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FORMULA
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E.g.f.: x + sum_{n =1 .. inf} a(n)*(x^(2n+1))/(2n+1)! = (f(0,x)*f(1,x)- f(2,x)*f(3,x)+ f(3,x))/(f(0,x)^2 - f(1,x)*f(3,x)), where f(j,x) = sum_{k = 0 .. inf} (x^(4k+j))/(4k+j)!, j = 0,1,2,3, is the j-th generalized hyperbolic function. - Peter Bala (pbala(AT)toucansurf.com), Jul 13 2007
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CROSSREFS
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Bisection of A058258.
Cf. A131453, A131454, A131455.
Adjacent sequences: A005978 A005979 A005980 this_sequence A005982 A005983 A005984
Sequence in context: A092085 A028844 A127135 this_sequence A024272 A052615 A052791
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KEYWORD
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nonn
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AUTHOR
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njas
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