A009749 Expansion of e.g.f. tan(x)*tan(sinh(x)), even powers only.

0, 2, 20, 438, 17128, 1048874, 92901500, 11253292638, 1788824156368, 361485870772562, 90552477245862884, 27548125826770266630, 10006652421435397898680, 4278388540712731489923194, 2127009769120013449890941516, 1216712823253198094167750050990

Offset

0,2

Links

G. C. Greubel, Table of n, a(n) for n = 0..230

Formula

a(n) ~ (2*n)! * 4 * tan(arcsinh(Pi/2)) / (sqrt(4+Pi^2) * arcsinh(Pi/2)^(2*n+1)). - Vaclav Kotesovec, Jan 24 2015

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Tan[x]*Tan[Sinh[x]], {x, 0, nn}], x]Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Nov 30 2011 *)

Prog

(PARI) x='x+O('x^50); v=Vec(serlaplace(tan(x)*tan(sinh(x)))); concat([0], vector(#v\2, n, v[2*n-1])) \\ G. C. Greubel, Feb 12 2018

Crossrefs

Sequence in context: A165554 A366447 A009746 * A012533 A009160 A188811

Adjacent sequences: A009746 A009747 A009748 * A009750 A009751 A009752

Keyword

nonn

Author

R. H. Hardin

Extensions

Extended and signs tested by Olivier Gérard, Mar 15 1997

Status

approved