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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 20 |
| 2 | 924 |
| 3 | 48620 |
| 4 | 2704156 |
| 5 | 155117520 |
| 6 | 9075135300 |
| 7 | 538257874440 |
| 8 | 32247603683100 |
| 9 | 1946939425648112 |
| 10 | 118264581564861424 |
| 11 | 7219428434016265740 |
| 12 | 442512540276836779204 |
| 13 | 27217014869199032015600 |
| 14 | 1678910486211891090247320 |
| 15 | 103827421287553411369671120 |
| 16 | 6435067013866298908421603100 |
[1,20,924,48620,2704156,155117520,9075135300, 538257874440,32247603683100,1946939425648112, 118264581564861424,7219428434016265740, 442512540276836779204,27217014869199032015600, 1678910486211891090247320, 103827421287553411369671120, 6435067013866298908421603100] |