A003700 - OEIS

A003700

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

1, -1, -19, 475, 1753, -1109769, 70784325, 2711086547, -1376283649103, 148592152807663, 21812320857733789, -12754009647903010101, 1675171082535404962441, 847081835857552788679655

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OFFSET

0,3

REFERENCES

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

LINKS

Table of n, a(n) for n=0..13.

MATHEMATICA

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

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 *)

CROSSREFS

Sequence in context: A081686 A284163 A218477 * A093975 A159248 A348321

Adjacent sequences: A003697 A003698 A003699 * A003701 A003702 A003703

KEYWORD

sign

AUTHOR

R. H. Hardin, N. J. A. Sloane, Simon Plouffe

STATUS

approved