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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 19 |
| 5 | 131 |
| 6 | 1156 |
| 7 | 12622 |
| 8 | 166825 |
| 9 | 2600677 |
| 10 | 47038456 |
| 11 | 974165336 |
| 12 | 22829939089 |
| 13 | 599668759483 |
| 14 | 17512623094240 |
| 15 | 564613124026876 |
| 16 | 19972670155565761 |
| 17 | 771019774737952313 |
| 18 | 32326390781950804048 |
[1,1,1,4,19,131,1156,12622,166825,2600677, 47038456,974165336,22829939089,599668759483, 17512623094240,564613124026876,19972670155565761, 771019774737952313,32326390781950804048] |