>>727

 a[1] = -1/2,
 a[n] = 2a[n-1] + (n/2)^2 + n, (n:偶数)
    = (1/2)a[n-1] - (n+1)/4, (n:奇数)

 -1/2, 0, -1, 6, 3/2, 18, 7, 38, 33/2, 68, 31, 110, 103/2, 166, 79, 238, 229, 328, 159, 438, 427/2, 570, 279, 726,