from mpmath import mp mp.dps = 110 def hyper3f2_half_series(z, tol=None, max_terms=200000): if tol is None: tol = mp.eps s = mp.mpf(1) term = mp.mpf(1) for n in range(1, max_terms + 1): term *= ((n - mp.mpf('0.5'))**3) * z / (n**3) s_new = s + term if abs(term) <= tol * abs(s_new): return s_new s = s_new raise RuntimeError("Series did not converge within max_terms") def compute(): # Non-trivial algebraic argument z = mp.sqrt(2) - 1 with mp.workdps(140): # Clausen identity: 3F2(1/2,1/2,1/2;1,1;z) = [2F1(1/4,1/4;1;z)]^2 f2 = mp.hyper([mp.mpf(1)/4, mp.mpf(1)/4], [mp.mpf(1)], z) val_clausen = f2 * f2 # Independent computation by direct series for 3F2 val_series = hyper3f2_half_series(z, tol=mp.mpf('1e-130')) # Return the more stable average if they agree closely if abs(val_clausen - val_series) <= mp.mpf('1e-120') * max(1, abs(val_clausen), abs(val_series)): return mp.mpf((val_clausen + val_series) / 2) return mp.mpf(val_clausen) if __name__ == "__main__": print(str(compute()))