# erfc(x) is the complementary error function; # erfc(n,x) is the nth Iterated integrals of the complementary error function, the -nth derivative; # erfc(n_,x_) := int(erfc(n-1,t),t,x,inf); erfc(0,x_):=erfc(x); erfc(-1,x_):= 2/sqrt(pi)*exp(-x^2); erfc(1,x_):=x-exp(-x^2)*pi^(-1/2)+x*erf(x); erfc(x_) := if(not(isnumber(x)),1-erf(x));