def binomial_coefficients(n):
    d = {(0, n): 1, (n, 0): 1}
    a = 1
    for k in range(1, n//2 + 1):
        a = (a * (n - k + 1))//k
        d[k, n - k] = d[n - k, k] = a
    return d
Return a dictionary containing pairs :math:`{(k1,k2) : C_kn}` where
dataset/ETHPy150Open sympy/sympy/sympy/ntheory/multinomial.py/binomial_coefficients