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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 20 |
| 5 | 100 |
| 6 | 612 |
| 7 | 4389 |
| 8 | 35688 |
| 9 | 325395 |
| 10 | 3288490 |
| 11 | 36489992 |
| 12 | 441093864 |
| 13 | 5770007009 |
| 14 | 81213878830 |
| 15 | 1223895060315 |
| 16 | 19662509071056 |
| 17 | 335472890422812 |
| 18 | 6057979285535388 |
| 19 | 115434096553014565 |
| 20 | 2314691409652237700 |
| 21 | 48723117262650147387 |
| 22 | 1074208020519710570054 |
[1,1,2,3,20,100,612,4389,35688,325395,3288490, 36489992,441093864,5770007009,81213878830, 1223895060315,19662509071056,335472890422812, 6057979285535388,115434096553014565, 2314691409652237700,48723117262650147387, 1074208020519710570054] |