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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 16 |
| 4 | 103 |
| 5 | 724 |
| 6 | 5381 |
| 7 | 41603 |
| 8 | 331251 |
| 9 | 2698123 |
| 10 | 22377963 |
| 11 | 188354172 |
| 12 | 1604864527 |
| 13 | 13815855427 |
| 14 | 119989316373 |
| 15 | 1050060125737 |
| 16 | 9250659021067 |
| 17 | 81973487875776 |
| 18 | 730180058911437 |
| 19 | 6534340375318637 |
| 20 | 58719824201731279 |
| 21 | 529668859086486941 |
[1,1,3,16,103,724,5381,41603,331251,2698123, 22377963,188354172,1604864527,13815855427, 119989316373,1050060125737,9250659021067, 81973487875776,730180058911437,6534340375318637, 58719824201731279,529668859086486941] |