b-spline recursion

A recursive function that computes the b-spline basis atoms, it's very compact

a function to compute the b-spline points on a grid
usage y = spline_recursion (u,n)
n is the order of the spline
u is the grid point
example:
t=linspace(-2,10,10000);
y1=spline_recursion (t,2);
y2=spline_recursion (t,3);
y3=spline_recursion (t,4);
y4=spline_recursion (t,10);
subplot(2,2,1), plot(t,y1), title('b-spline order = 2');
subplot(2,2,2), plot(t,y2), title('b-spline order = 3');
subplot(2,2,3), plot(t,y3), title('b-spline order = 4');
subplot(2,2,4), plot(t,y4), title('b-spline order = 10');