j_from_lambda

Usage:
    <j_from_lambda lambda j
computes j = 2^8 (lambda^2-lambda+1)^3 / lambda^2 (lambda-1)^2
Parameters:
            lambda = a number (from the base field)
Output values:
            j = 1x1 matrix containing a number.
This is the function invariant under lambda -->
            lambda, 1/lambda, 1-lambda, 1/(1-lambda)
    lambda/(lambda-1) , (lambda-1)/lambda.