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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 8 |
| 3 | 90 |
| 4 | 1312 |
| 5 | 23625 |
| 6 | 505116 |
| 7 | 12475596 |
| 8 | 348942336 |
| 9 | 10888165395 |
| 10 | 374606200000 |
| 11 | 14077548113398 |
| 12 | 573396296212224 |
| 13 | 25150850370412156 |
| 14 | 1181513742628738624 |
| 15 | 59165118490203450000 |
| 16 | 3145241884988171878400 |
| 17 | 176865209305943158023799 |
| 18 | 10486960289673977419520256 |
[1,1,8,90,1312,23625,505116,12475596,348942336, 10888165395,374606200000,14077548113398, 573396296212224,25150850370412156, 1181513742628738624,59165118490203450000, 3145241884988171878400,176865209305943158023799, 10486960289673977419520256] |