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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 10 |
| 6 | 20 |
| 7 | 175 |
| 8 | 2296 |
| 9 | 20244 |
| 10 | 134520 |
| 11 | 1016565 |
| 12 | 13527580 |
| 13 | 209970046 |
| 14 | 2785823404 |
| 15 | 33569936855 |
| 16 | 467250784560 |
| 17 | 8358652382760 |
| 18 | 159820481883696 |
| 19 | 2888819281378089 |
| 20 | 51781860691882740 |
| 21 | 1031576680142770930 |
| 22 | 23237341150372569220 |
| 23 | 543570375735294712651 |
[1,0,0,1,4,10,20,175,2296,20244,134520,1016565, 13527580,209970046,2785823404,33569936855, 467250784560,8358652382760,159820481883696, 2888819281378089,51781860691882740, 1031576680142770930,23237341150372569220, 543570375735294712651] |