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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 1 |
| 5 | 20 |
| 6 | 1680 |
| 7 | 1 |
| 8 | 70 |
| 9 | 34650 |
| 10 | 63063000 |
| 11 | 1 |
| 12 | 252 |
| 13 | 756756 |
| 14 | 11732745024 |
| 15 | 623360743125120 |
| 16 | 1 |
| 17 | 924 |
| 18 | 17153136 |
| 19 | 2308743493056 |
| 20 | 1370874167589326400 |
| 21 | 2670177736637149247308800 |
| 22 | 1 |
| 23 | 3432 |
| 24 | 399072960 |
| 25 | 472518347558400 |
| 26 | 3177459078523411968000 |
| 27 | 85722533226982363751829504000 |
| 28 | 7363615666157189603982585462030336000 |
[1,1,6,1,20,1680,1,70,34650,63063000,1,252,756756, 11732745024,623360743125120,1,924,17153136, 2308743493056,1370874167589326400, 2670177736637149247308800,1,3432,399072960, 472518347558400,3177459078523411968000, 85722533226982363751829504000, 7363615666157189603982585462030336000] |