>>74
　q[1] = 0,　q[2] = 2/7,　q[3] = 5/14,　q[4] = 12/35,　q[5] = 29/86　→　3/8,

[前スレ.609] から
　a[1] = 0,　a[2] = 1/3,　a[3] = 1/3,　a[4] = 12/35,　a[5] = 47/135　→ 1/e,

　a[n] = a[n-1] + {1/(2n-1)(2n-3)} a[n-2],