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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 18 |
| 5 | 160 |
| 6 | 1545 |
| 7 | 19131 |
| 8 | 273868 |
| 9 | 4463460 |
| 10 | 82561545 |
| 11 | 1695986875 |
| 12 | 38413504866 |
| 13 | 951203750718 |
| 14 | 25551218851249 |
| 15 | 740338919242755 |
| 16 | 23014265170565880 |
| 17 | 764047265130952456 |
| 18 | 26981593786255568913 |
| 19 | 1009915667787285212787 |
| 20 | 39938889756657408019390 |
[1,0,1,3,18,160,1545,19131,273868,4463460, 82561545,1695986875,38413504866,951203750718, 25551218851249,740338919242755,23014265170565880, 764047265130952456,26981593786255568913, 1009915667787285212787,39938889756657408019390] |