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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 10 |
| 4 | 65 |
| 5 | 371 |
| 6 | 3780 |
| 7 | 33552 |
| 8 | 472971 |
| 9 | 5736082 |
| 10 | 97047819 |
| 11 | 1547576394 |
| 12 | 32992294296 |
| 13 | 626527881617 |
| 14 | 15202246707840 |
| 15 | 352290010708120 |
| 16 | 9970739854456849 |
| 17 | 262225912049078193 |
| 18 | 8309425491887714632 |
| 19 | 250946978120046026219 |
| 20 | 8898019305511325083149 |
[1,1,3,10,65,371,3780,33552,472971,5736082, 97047819,1547576394,32992294296,626527881617, 15202246707840,352290010708120,9970739854456849, 262225912049078193,8309425491887714632, 250946978120046026219,8898019305511325083149] |