OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..423
FORMULA
a(n) = Sum_{m=0..n/2} ((4^(-m)*Sum_{j=m..n/2} (binomial(n+1,2*j+1)*((2*m+1)^(n-2*j-1)*sum(i=0..m+1/2, (2*i-2*m-1)^(2*j+1)*(-1)^(j+1-i)*binomial(2*m+1,i)))))). - Vladimir Kruchinin, Jun 30 2011
EXAMPLE
arctan(sin(x)*exp(x)) = x + (2/2!)*x^2 - (24/4!)*x^4 - (140/5!)*x^5 - (8/6!)*x^6 + ...
MATHEMATICA
CoefficientList[Series[ArcTan[Sin[x]*Exp[x]], {x, 0, 20}], x]*Range[0, 20]! (* Vaclav Kotesovec, Jan 02 2014 *)
PROG
(Maxima)
a(n):=sum((4^(-m)*sum(binomial(n+1, 2*j+1)*((2*m+1)^(n-2*j-1)*sum((2*i-2*m-1)^(2*j+1)*(-1)^(j+1-i)*binomial(2*m+1, i), i, 0, m+1/2)), j, m, (n)/2)), m, 0, (n)/2); /* Vladimir Kruchinin, Jun 30 2011 */
(PARI) x='x+O('x^30); concat([0], Vec(serlaplace(atan(sin(x)*exp(x))))) \\ G. C. Greubel, Oct 26 2018
(Magma) m:=30; R<x>:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!( Arctan(Sin(x)*Exp(x)) )); [0] cat [Factorial(n)*b[n]: n in [1..m-1]]; // G. C. Greubel, Oct 26 2018
CROSSREFS
KEYWORD
sign
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
EXTENSIONS
Missing a(0)=0 prepended by Vaclav Kotesovec, Jan 02 2014
STATUS
approved