load(simplify_sum)$
simplify_sum(...)
Unfortunately, in your case, simplify_sum gives the result as the
hypergeometric function %f[0,2]([],[1/3,2/3],x^3/27), which may be correct,
but isn't very helpful.
Similarly, simplify_sum( sum( (-1)^n*x^(2*n)/(2*n)!, n,0,inf ) )
gives sqrt(%pi)*bessel_j(-1/2,x)*sqrt(x)/sqrt(2) rather than cos(x)....
Correct, but not as nice.
-s
On Mon, Jun 4, 2012 at 5:05 PM, Aleksas Domarkas <aleksasd873 at gmail.com>wrote:
> sum(x^(3*n)/(3*n)!,n,0,inf) ?