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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 15 |
| 4 | 420 |
| 5 | 36 |
| 6 | 1386 |
| 7 | 36036 |
| 8 | 40040 |
| 9 | 6126120 |
| 10 | 2116296 |
| 11 | 255816 |
| 12 | 267711444 |
| 13 | 3346393050 |
| 14 | 1745944200 |
| 15 | 6850263420 |
| 16 | 14440355289360 |
| 17 | 1604483921040 |
| 18 | 3800093497200 |
| 19 | 2671465728531600 |
| 20 | 534293145706320 |
| 21 | 952435607563440 |
| 22 | 941958815880242160 |
| 23 | 362291852261631600 |
[1,6,15,420,36,1386,36036,40040,6126120,2116296, 255816,267711444,3346393050,1745944200,6850263420, 14440355289360,1604483921040,3800093497200, 2671465728531600,534293145706320,952435607563440, 941958815880242160,362291852261631600] |