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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 63 |
| 3 | 560 |
| 4 | 4984 |
| 5 | 44352 |
| 6 | 394688 |
| 7 | 3512320 |
| 8 | 31256064 |
| 9 | 278147072 |
| 10 | 2475225088 |
| 11 | 22026977280 |
| 12 | 196017618944 |
| 13 | 1744356769792 |
| 14 | 15522995109888 |
| 15 | 138138815037440 |
| 16 | 1229294481178624 |
| 17 | 10939466369728512 |
| 18 | 97350086807257088 |
[1,7,63,560,4984,44352,394688,3512320,31256064, 278147072,2475225088,22026977280,196017618944, 1744356769792,15522995109888,138138815037440, 1229294481178624,10939466369728512, 97350086807257088] |