def test_issue_20286():
n, p = symbols('n p')
B = Binomial('B', n, p)
k = Dummy('k', integer=True)
eq = Sum(
Piecewise(
(-p**k * (1 - p)**(-k + n) *
log(p**k * (1 - p)**(-k + n) * binomial(n, k)) * binomial(n, k),
(k >= 0) & (k <= n)), (nan, True)), (k, 0, n))
assert eq.dummy_eq(H(B))
