By definition, the partial derivative of this function with respect to x (with a constant) is f(). The complete derivative, however, is dF().
function F
extends Modelica.Icons.Function;
input Real x "Argument" annotation(
Dialog(__Dymola_label = "<html><i>x</i></html>"));
input Real a[:] "Coefficients" annotation(
Dialog(__Dymola_label = "<html><i>a</i></html>"));
input Integer n = 0 "Power associated with the first term (before integral)" annotation(
Dialog(__Dymola_label = "<html><i>n</i></html>"));
output Real F "Integral" annotation(
Dialog(__Dymola_label = "<html><i>F</i></html>"));
end F;