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| n | a(n) |
|---|---|
| 3 | 1 |
| 4 | 3 |
| 5 | 12 |
| 6 | 36 |
| 7 | 383 |
| 8 | 1560 |
| 9 | 19162 |
| 10 | 97680 |
| 11 | 1804643 |
| 12 | 4082400 |
| 13 | 207316912 |
| 14 | 1186043040 |
| 15 | 25595629200 |
| 16 | 266545072080 |
| 17 | 6282386337194 |
| 18 | 26013379392000 |
| 19 | 1682187039875545 |
| 20 | 11884755543091200 |
| 21 | 396276417247253760 |
| 22 | 5491416186030297600 |
[1,3,12,36,383,1560,19162,97680,1804643,4082400, 207316912,1186043040,25595629200,266545072080, 6282386337194,26013379392000,1682187039875545, 11884755543091200,396276417247253760, 5491416186030297600] |