import numpy as np
data = [1487, 1847, 4817, 4871, 7481, 7841, 8147, 8741]
data = np.array(data)
i = data.reshape(-1, 1, 1)
j = data.reshape(1, -1, 1)
k = data.reshape(1, 1, -1)
indices = np.where(i + j - 2 * k == 0)
for i, k, j in zip(*indices):
if i < j < k:
print(data[[i, j, k]])
for i in range(20):
print(i, 9 ** (i % 2), 9 ** i)
0 1 1
1 9 9
2 1 81
3 9 729
4 1 6561
5 9 59049
6 1 531441
7 9 4782969
8 1 43046721
9 9 387420489
10 1 3486784401
11 9 31381059609
12 1 282429536481
13 9 2541865828329
14 1 22876792454961
15 9 205891132094649
16 1 1853020188851841
17 9 16677181699666569
18 1 150094635296999121
19 9 1350851717672992089