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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 21 |
| 3 | 1897 |
| 4 | 515152 |
| 5 | 334109776 |
| 6 | 444139428096 |
| 7 | 1086286396836096 |
| 8 | 4512504650332962816 |
| 9 | 29936169668265688498176 |
| 10 | 302049012729161725378560000 |
| 11 | 4454989520743493117582376960000 |
| 12 | 92950790729047047971705255362560000 |
| 13 | 2668743485551052734888225563381596160000 |
[0,1,21,1897,515152,334109776,444139428096, 1086286396836096,4512504650332962816, 29936169668265688498176, 302049012729161725378560000, 4454989520743493117582376960000, 92950790729047047971705255362560000, 2668743485551052734888225563381596160000] |