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A003700 Expansion of tan(x /cosh(x)).
(Formerly M5080)
3

%I M5080

%S 1,-1,-19,475,1753,-1109769,70784325,2711086547,-1376283649103,

%T 148592152807663,21812320857733789,-12754009647903010101,

%U 1675171082535404962441,847081835857552788679655

%N Expansion of tan(x /cosh(x)).

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%t Tan[ x/Cosh[ x ] ] (* Odd Part *)

%t nn = 20; Table[(CoefficientList[Series[Tan[x*Sech[x]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* _Vaclav Kotesovec_, Feb 16 2015 *)

%K sign

%O 0,3

%A _R. H. Hardin_, _N. J. A. Sloane_, _Simon Plouffe_

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Last modified September 19 08:54 EDT 2021. Contains 347556 sequences. (Running on oeis4.)