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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 27 |
| 4 | 254 |
| 5 | 3048 |
| 6 | 44328 |
| 7 | 755681 |
| 8 | 14750646 |
| 9 | 323999500 |
| 10 | 7901623624 |
| 11 | 211690439030 |
| 12 | 6176393964684 |
| 13 | 194847458672328 |
| 14 | 6606138879434128 |
| 15 | 239466033046020357 |
| 16 | 9239284257332493478 |
| 17 | 377948418993992417644 |
| 18 | 16335430070738649950536 |
| 19 | 743711790322786003051882 |
[1,1,4,27,254,3048,44328,755681,14750646, 323999500,7901623624,211690439030,6176393964684, 194847458672328,6606138879434128, 239466033046020357,9239284257332493478, 377948418993992417644,16335430070738649950536, 743711790322786003051882] |