var('x')
y = function('y',x)  
y=0
l=[]
m=[]
sol=function('sol',x)

for i in range(4):
    sol=x+integral(y**2,x,0,x)
    y=sol
    l.append(y)
    plot(y,x,-3,3)
    print "y(",i,")=",show(y)