A024342 Expansion of e.g.f. tanh(x)*tan(x), coefficients of powers x^(4*n+2).

2, 112, 92672, 365688832, 4411282030592, 127206964253949952, 7496936195881447718912, 809926025985929119868649472, 148071124873925782667263194693632, 43087047288444223765736160658186043392, 19011875896715283767147325248912471990730752

Offset

0,1

Links

G. C. Greubel, Table of n, a(n) for n = 0..120

Formula

a(n) = 2 * A009837(n).

Mathematica

With[{nn=40}, Take[CoefficientList[Series[Tanh[x]Tan[x], {x, 0, nn}], x] Range[0, nn-2]!, {3, -1, 4}]] (* Harvey P. Dale, May 02 2012 *)

Prog

(Magma)
m:=50; R<x>:=PowerSeriesRing(Rationals(), m);
b:= Coefficients(R!(Laplace( Tan(x)*Tanh(x) )));
[b[4*n-3]: n in [1..Floor((m-2)/4)]]; // G. C. Greubel, Jan 31 2022
(Sage) [factorial(4*n+2)*( tanh(x)*tan(x) ).series(x, 4*n+3).list()[4*n+2] for n in (0..20)] # G. C. Greubel, Jan 31 2022

Crossrefs

Cf. A000182, A009837, A296628.

Sequence in context: A341782 A024341 A012528 * A225333 A012525 A165975

Adjacent sequences: A024339 A024340 A024341 * A024343 A024344 A024345

Keyword

nonn

Author

R. H. Hardin

Extensions

Extended and signs tested by Olivier Gérard, Mar 15 1997

More terms from Harvey P. Dale, May 02 2012

Status

approved