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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 7 |
| 3 | 49 |
| 4 | 344 |
| 5 | 2408 |
| 6 | 16856 |
| 7 | 117993 |
| 8 | 825951 |
| 9 | 5781657 |
| 10 | 40471600 |
| 11 | 283301200 |
| 12 | 1983108400 |
| 13 | 13881758801 |
| 14 | 97172311607 |
| 15 | 680206181249 |
| 16 | 4761443268744 |
| 17 | 33330102881208 |
| 18 | 233310720168456 |
| 19 | 1633175041179193 |
| 20 | 11432225288254351 |
| 21 | 80025577017780457 |
| 22 | 560179039124463200 |
| 23 | 3921253273871242400 |
[1,7,49,344,2408,16856,117993,825951,5781657, 40471600,283301200,1983108400,13881758801, 97172311607,680206181249,4761443268744, 33330102881208,233310720168456,1633175041179193, 11432225288254351,80025577017780457, 560179039124463200,3921253273871242400] |