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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 18 |
| 4 | 159 |
| 5 | 1872 |
| 6 | 27585 |
| 7 | 488736 |
| 8 | 10122273 |
| 9 | 240029568 |
| 10 | 6413759739 |
| 11 | 190698235200 |
| 12 | 6244960476447 |
| 13 | 223354435468032 |
| 14 | 8662843993599081 |
| 15 | 362162307560207616 |
| 16 | 16235331377066437185 |
| 17 | 776899798554908971008 |
| 18 | 39526189786699908619635 |
| 19 | 2130538920122365706916864 |
[1,1,3,18,159,1872,27585,488736,10122273, 240029568,6413759739,190698235200,6244960476447, 223354435468032,8662843993599081, 362162307560207616,16235331377066437185, 776899798554908971008,39526189786699908619635, 2130538920122365706916864] |