A024257 Expansion of tanh(tan(x)*x)/2.

0, 1, 4, -72, -5632, -161920, 18173952, 4194147328, 310213328896, -84365860995072, -39813939519815680, -5549928926785306624, 2813587774502929956864, 2234702652489178135134208, 497733049858403607865458688

Offset

0,3

Links

Table of n, a(n) for n=0..14.

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Tanh[Tan[x]*x]/2 , {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Apr 27 2016 *)

Crossrefs

Cf. A009817.

Sequence in context: A076744 A177392 A158269 * A152653 A344693 A172478

Adjacent sequences: A024254 A024255 A024256 * A024258 A024259 A024260

Keyword

sign

Author

R. H. Hardin

Extensions

Extended with signs Mar 1997

Prior Mathematica program deleted by Harvey P. Dale, Apr 27 2016

Status

approved