plots.sagews

# Bicorn http://mathworld.wolfram.com/Bicorn.html
var('x,y,a')
a=2
v=sum(implicit_plot(y^2*(a^2-x^2)==(x^2+2*a*y-a^2)^2,(x,-4,4),(y,-4,4)) for a in [-3,-2,..,3])
v.show()

(x, y, a)