A012030 - OEIS

%I #10 Dec 04 2024 19:23:26

%S 1,-2,16,-440,20224,-1582976,178612864,-27969867008,5765737517056,

%T -1516228355846144,495092243779256320,-196552136456231321600,

%U 93232152295610535018496,-52074797114273752377786368

%N arctan(sin(sinh(x))) = x - 2/3!*x^3 +16/5!*x^5 - 440/7!*x^7 + 20224/9!*x^9 - ....

%C a(n) appears to be divisible by 2^n, with the factor 1, -1, 4, -55, 1264, -49468, 2790826, -218514586, 22522412176,.... - _Ralf Stephan_, Aug 14 2013

%t With[{nn=30},Take[CoefficientList[Series[ArcTan[Sin[Sinh[x]]],{x,0,nn}],x] Range[0,nn-1]!,{2,-1,2}]] (* _Harvey P. Dale_, Dec 04 2024 *)

%K sign

%O 0,2

%A Patrick Demichel (patrick.demichel(AT)hp.com)