vsota
5 + (4*(1/(2*n^2) - 1/(2*n)))/125 + (8*(1/(6*n^3) - 1/(2*n^2) + 1/(3*n)))/
  3125 + 2/(5*n)
17/18
-x/4 + x^2/4 - C[1]/(2*E^(2*x)) + C[2]