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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 9 |
| 3 | 52 |
| 4 | 413 |
| 5 | 3916 |
| 6 | 41077 |
| 7 | 481384 |
| 8 | 6198425 |
| 9 | 86430160 |
| 10 | 1296040841 |
| 11 | 20763245944 |
| 12 | 353272341061 |
| 13 | 6353672109760 |
| 14 | 120315348389069 |
| 15 | 2390488408994536 |
| 16 | 49682962883210033 |
| 17 | 1077292416660660736 |
| 18 | 24313317132393295633 |
| 19 | 569937590287796925784 |
| 20 | 13850459183086300341341 |
[1,1,9,52,413,3916,41077,481384,6198425,86430160, 1296040841,20763245944,353272341061,6353672109760, 120315348389069,2390488408994536, 49682962883210033,1077292416660660736, 24313317132393295633,569937590287796925784, 13850459183086300341341] |