A024236 Expansion of log(1+tan(x)*x)/2.

0, 1, -2, 48, -1040, 62720, -4314624, 498003968, -70081316864, 13529482592256, -3175495421788160, 933402531586899968, -326784893253162369024, 136568449424117316190208, -66517446960602151366164480

Offset

0,3

Links

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

Formula

E.g.f. of aerated sequence: Sum(n>=0, a(n)*x^(2*n)/(2*n)!) = log(1+tan(x)*x)/2. - Robert Israel, Jun 29 2015

Maple

S:= series(log(1+tan(x)*x)/2, x, 101): seq(coeff(S, x, 2*j)*(2*j)!, j=0..50); # Robert Israel, Jun 29 2015

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Log[1+Tan[x]x]/2, {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jun 24 2018 *)

Crossrefs

Cf. A009379.

Cf. A101921.

Sequence in context: A013523 A260846 A009670 * A119703 A012803 A135394

Adjacent sequences: A024233 A024234 A024235 * A024237 A024238 A024239

Keyword

sign

Author

R. H. Hardin

Extensions

Extended with signs, Mar 1997

Previous Mathematica program replaced by Harvey P. Dale, Jun 24 2018

Status

approved