A009823 Expansion of tanh(tanh(x)*tan(x))/2.

1, -64, 6016, 182844416, -1001405579264, -33574129505665024, 1883390165749948481536, 20340448295605095121289216, -36112647755760335076622057078784

Offset

0,2

Links

Table of n, a(n) for n=0..8.

Mathematica

With[{nn=40}, Take[CoefficientList[Series[Tanh[Tanh[x]*Tan[x]]/2, {x, 0, nn}], x] Range[0, nn-2]!, {3, -1, 4}]] (* Harvey P. Dale, Mar 31 2019 *)

Crossrefs

Cf. A012673.

Sequence in context: A316821 A317571 A240346 * A222100 A223265 A266631

Adjacent sequences: A009820 A009821 A009822 * A009824 A009825 A009826

Keyword

sign

Author

R. H. Hardin

Extensions

Extended with signs Mar 1997

Previous Mathematica program replaced by Harvey P. Dale, Mar 31 2019

Status

approved