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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 17 |
| 5 | 86 |
| 6 | 517 |
| 7 | 3620 |
| 8 | 28961 |
| 9 | 260650 |
| 10 | 2606501 |
| 11 | 28671512 |
| 12 | 344058145 |
| 13 | 4472755886 |
| 14 | 62618582405 |
| 15 | 939278736076 |
| 16 | 15028459777217 |
| 17 | 255483816212690 |
| 18 | 4598708691828421 |
| 19 | 87375465144740000 |
| 20 | 1747509302894800001 |
| 21 | 36697695360790800022 |
| 22 | 807349297937397600485 |
[0,1,4,17,86,517,3620,28961,260650,2606501, 28671512,344058145,4472755886,62618582405, 939278736076,15028459777217,255483816212690, 4598708691828421,87375465144740000, 1747509302894800001,36697695360790800022, 807349297937397600485] |