A024236 - OEIS

%I #18 Jun 24 2018 12:28:17

%S 0,1,-2,48,-1040,62720,-4314624,498003968,-70081316864,13529482592256,

%T -3175495421788160,933402531586899968,-326784893253162369024,

%U 136568449424117316190208,-66517446960602151366164480

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

%F 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

%p 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

%t 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 *)

%Y Cf. A009379.

%Y Cf. A101921.

%K sign

%O 0,3

%A _R. H. Hardin_

%E Extended with signs, Mar 1997

%E Previous Mathematica program replaced by _Harvey P. Dale_, Jun 24 2018