having trouble creating fractal picture

Xsubk + 1 = Ysubk*(1 + sin(.7Xsubk) - 1.2*sqrt(|Xsubk|)

Ysubk +1 = .21 - Xsubk

for k = 1:1:19999

I'm not sure how to initiate plotting these points. I don't know how to deal with the subscripts "subk". Any help would be greatly appreciated. Thank You

[Joseph]

Figured it out:

x(1)=0;
y(1)=0;

for k = 1:1:19999
    x(k+1) = y(k)*(1+sin(.7*x(k))) - 1.2*sqrt(abs(x(k)));
    y(k+1) = .21 - x(k);
end

plot(x,y,'o','markersize',2)