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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 44 |
| 5 | 381 |
| 6 | 4332 |
| 7 | 60691 |
| 8 | 1012664 |
| 9 | 19610233 |
| 10 | 432457640 |
| 11 | 10701243741 |
| 12 | 293661065788 |
| 13 | 8851373201919 |
| 14 | 290711372717976 |
| 15 | 10334165623697259 |
| 16 | 395320344293410544 |
| 17 | 16192709833199300337 |
| 18 | 707125993042984343136 |
| 19 | 32795665902734099555845 |
| 20 | 1609908874238209683872480 |
[1,1,2,7,44,381,4332,60691,1012664,19610233, 432457640,10701243741,293661065788,8851373201919, 290711372717976,10334165623697259, 395320344293410544,16192709833199300337, 707125993042984343136,32795665902734099555845, 1609908874238209683872480] |