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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 5 |
| 4 | 16 |
| 5 | 84 |
| 6 | 512 |
| 7 | 3572 |
| 8 | 28080 |
| 9 | 256820 |
| 10 | 2553728 |
| 11 | 28064776 |
| 12 | 337319944 |
| 13 | 4385615904 |
| 14 | 61255920936 |
| 15 | 921584068648 |
| 16 | 14720437293952 |
| 17 | 250190161426720 |
| 18 | 4507229152534944 |
| 19 | 85630125536152160 |
| 20 | 1711040906290680448 |
| 21 | 35969941361999955392 |
| 22 | 790961860293623563648 |
[1,1,1,5,16,84,512,3572,28080,256820,2553728, 28064776,337319944,4385615904,61255920936, 921584068648,14720437293952,250190161426720, 4507229152534944,85630125536152160, 1711040906290680448,35969941361999955392, 790961860293623563648] |