vsota
3 + (1/(2*n^2) - 1/(2*n))/3 + (1/(6*n^3) - 1/(2*n^2) + 1/(3*n))/9 + n^(-1)
11/24
-x/4 - x^2/4 + (E^(2*x)*C[1])/2 + C[2]