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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 20 |
| 4 | 309 |
| 5 | 3499 |
| 6 | 33692 |
| 7 | 309493 |
| 8 | 2721044 |
| 9 | 23193721 |
| 10 | 193520569 |
| 11 | 1587628975 |
| 12 | 12850623027 |
| 13 | 102883527733 |
| 14 | 816204241881 |
| 15 | 6425192293124 |
| 16 | 50243446084946 |
| 17 | 390619259367639 |
| 18 | 3021431489931709 |
| 19 | 23265194042723056 |
| 20 | 178420043485112107 |
[0,1,20,309,3499,33692,309493,2721044,23193721, 193520569,1587628975,12850623027,102883527733, 816204241881,6425192293124,50243446084946, 390619259367639,3021431489931709, 23265194042723056,178420043485112107] |