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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 24 |
| 6 | 120 |
| 7 | 720 |
| 8 | 2520 |
| 9 | 13440 |
| 10 | 90720 |
| 11 | 725760 |
| 12 | 6652800 |
| 13 | 68428800 |
| 14 | 444787200 |
| 15 | 4151347200 |
| 16 | 46702656000 |
| 17 | 597793996800 |
| 18 | 8468748288000 |
| 19 | 130660687872000 |
| 20 | 1241276534784000 |
| 21 | 16550353797120000 |
| 22 | 260668072304640000 |
| 23 | 4587758072561664000 |
| 24 | 87932029724098560000 |
[1,1,1,2,6,24,120,720,2520,13440,90720,725760, 6652800,68428800,444787200,4151347200,46702656000, 597793996800,8468748288000,130660687872000, 1241276534784000,16550353797120000, 260668072304640000,4587758072561664000, 87932029724098560000] |