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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 54 |
| 3 | 441 |
| 4 | 3724 |
| 5 | 32130 |
| 6 | 281359 |
| 7 | 2490695 |
| 8 | 22231341 |
| 9 | 199723668 |
| 10 | 1803710336 |
| 11 | 16359723198 |
| 12 | 148919995615 |
| 13 | 1359760296769 |
| 14 | 12448518709446 |
| 15 | 114227100633785 |
| 16 | 1050254412280420 |
| 17 | 9673701429423411 |
| 18 | 89244021409649401 |
| 19 | 824484497216920684 |
| 20 | 7626792613840800615 |
[1,7,54,441,3724,32130,281359,2490695,22231341, 199723668,1803710336,16359723198,148919995615, 1359760296769,12448518709446,114227100633785, 1050254412280420,9673701429423411, 89244021409649401,824484497216920684, 7626792613840800615] |