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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 39 |
| 4 | 648 |
| 5 | 15465 |
| 6 | 483240 |
| 7 | 18685905 |
| 8 | 861282832 |
| 9 | 46085893011 |
| 10 | 2807152825020 |
| 11 | 191731595897600 |
| 12 | 14510053796849640 |
| 13 | 1205013817282706730 |
| 14 | 108941005329522201360 |
| 15 | 10650027832902977866245 |
| 16 | 1119401271751383414197280 |
| 17 | 125879457463215695125460535 |
[1,1,4,39,648,15465,483240,18685905,861282832, 46085893011,2807152825020,191731595897600, 14510053796849640,1205013817282706730, 108941005329522201360,10650027832902977866245, 1119401271751383414197280, 125879457463215695125460535] |