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| n | a(n) |
|---|---|
| 1 | 20 |
| 2 | 400 |
| 3 | 2340 |
| 4 | 13200 |
| 5 | 87744 |
| 6 | 475984 |
| 7 | 2330037 |
| 8 | 11635558 |
| 9 | 55554808 |
| 10 | 251535759 |
| 11 | 1124853720 |
| 12 | 4944356292 |
| 13 | 21187341735 |
| 14 | 89511994640 |
| 15 | 374050079444 |
| 16 | 1542084294888 |
| 17 | 6290403091560 |
| 18 | 25452983767264 |
| 19 | 102144395660496 |
[20,400,2340,13200,87744,475984,2330037,11635558, 55554808,251535759,1124853720,4944356292, 21187341735,89511994640,374050079444, 1542084294888,6290403091560,25452983767264, 102144395660496] |