#set terminal postscript eps color
#set output "kukei.eps"
t(x,k) = 4/(pi*(2*k-1))*sin((2*k-1)*x)
series(x,n) = (n>0 ? t(x,n) + series(x,n-1) : 0)
f(x)=(x>0 ? 1 : -1)
set xrange [-pi:pi] 
plot series(x,5), f(x)