indep_symbolic.py -- exact expansion of P_n over Z
n=3: expanded 12 monomial products; nonzero coefficients in P_n: 0; control 1 (without (-1)^d): 6; control 2 (random weights): 6
n=4: expanded 360 monomial products; nonzero coefficients in P_n: 0; control 1 (without (-1)^d): 0; control 2 (random weights): 102
n=5: expanded 21600 monomial products; nonzero coefficients in P_n: 0; control 1 (without (-1)^d): 0; control 2 (random weights): 2200
n=6: expanded 1995840 monomial products; nonzero coefficients in P_n: 0; control 1 (without (-1)^d): 41808; control 2 (random weights): 68120
n=7: expanded 273067200 monomial products; nonzero coefficients in P_n: 0; control 1 (without (-1)^d): 1682828; control 2 (random weights): 2539068
P_n is the zero polynomial over Z for n = 3..7 (controls nonzero).  elapsed 379.9s
