3820.sagews

def f(x,y):
    if gcd(x,y)==1:
        return 1
    else:
        return 0;

def graf(b,a):
    M=matrix(a+1,a+1,lambda x, y: f(x,y))
    import numpy
    A=numpy.array(M)
    G=Graph(A)
    for i in range(0,b):
        G.delete_vertex(i)
    return G.show()

graf(1,20)