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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 10 |
| 4 | 70 |
| 5 | 656 |
| 6 | 7442 |
| 7 | 99280 |
| 8 | 1515190 |
| 9 | 26038016 |
| 10 | 497227682 |
| 11 | 10445708800 |
| 12 | 239394707110 |
| 13 | 5943715352576 |
| 14 | 158922998335922 |
| 15 | 4552807055288320 |
| 16 | 139123511874743830 |
| 17 | 4517007538261262336 |
| 18 | 155283277843358756162 |
| 19 | 5634815061983539363840 |
| 20 | 215234080472925069593350 |
[1,1,2,10,70,656,7442,99280,1515190,26038016, 497227682,10445708800,239394707110,5943715352576, 158922998335922,4552807055288320, 139123511874743830,4517007538261262336, 155283277843358756162,5634815061983539363840, 215234080472925069593350] |