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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 10 |
| 6 | 75 |
| 7 | 560 |
| 8 | 4550 |
| 9 | 41076 |
| 10 | 410970 |
| 11 | 4521000 |
| 12 | 54252495 |
| 13 | 705283150 |
| 14 | 9873965101 |
| 15 | 148109477880 |
| 16 | 2369751647900 |
| 17 | 40285778016680 |
| 18 | 725144004303300 |
| 19 | 13777736081766576 |
| 20 | 275554721635336365 |
| 21 | 5786649154342069650 |
| 22 | 127306281395525539615 |
| 23 | 2928044472097087420000 |
[0,0,0,0,1,10,75,560,4550,41076,410970,4521000, 54252495,705283150,9873965101,148109477880, 2369751647900,40285778016680,725144004303300, 13777736081766576,275554721635336365, 5786649154342069650,127306281395525539615, 2928044472097087420000] |