>    restart;

>    u50 := (x,y) -> Sum(((4/(n*Pi) - 2/(n*Pi)*(-1)^n)* cos( 2*n*y) + (1-(-1)^n)/(n*n*Pi)* sin(2*n*y)) *sin(n/2*x), n=1..50);
plot3d( u50(x,y), x=-4*Pi..4*Pi, y=0..6, labels =[`x`, `time`, `u(x,t)`], axes=FRAMED, style=patchcontour, contours=20);

u50 := proc (x, y) options operator, arrow; Sum(((4/n/Pi-2/n/Pi*(-1)^n)*cos(2*n*y)+(1-(-1)^n)/n/n/Pi*sin(2*n*y))*sin(1/2*n*x),n = 1 .. 50) end proc

[Maple Plot]

>   

>    u50 := (x,y) -> Sum(((4/(n*Pi) - 2/(n*Pi)*(-1)^n)* cos( 2*n*y) + (1-(-1)^n)/(n*n*Pi)* sin(2*n*y)) *sin(n/2*x), n=1..50);
plot3d( u50(x,y), x=-4*Pi..4*Pi, y=0..6, labels =[`x`, `time`, `u(x,t)`], axes=FRAMED, style=patchcontour, contours=20);

u50 := proc (x, y) options operator, arrow; Sum(((4/n/Pi-2/n/Pi*(-1)^n)*cos(2*n*y)+(1-(-1)^n)/n/n/Pi*sin(2*n*y))*sin(1/2*n*x),n = 1 .. 50) end proc

[Maple Plot]

>