>>3
p_n / q_n → {(1-π/4)p_0 + (π/4)p_1} / {(1-π/4)q_0 + (π/4)q_1},

特に q_0 = q_1 = 1 のときは

p_n / q_n → (1-π/4)p_0 + (π/4)p_1 = 4-π = 0.8584073464102…