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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 10 |
| 6 | 60 |
| 7 | 595 |
| 8 | 4536 |
| 9 | 34524 |
| 10 | 361320 |
| 11 | 4333725 |
| 12 | 51214460 |
| 13 | 651628406 |
| 14 | 9448719644 |
| 15 | 146868322055 |
| 16 | 2376666773040 |
| 17 | 41077757951000 |
| 18 | 762599081332176 |
| 19 | 14918668387075449 |
| 20 | 305774990501285940 |
| 21 | 6602482711971622210 |
| 22 | 149921553418087172260 |
| 23 | 3557552268845721893131 |
[1,0,0,1,4,10,60,595,4536,34524,361320,4333725, 51214460,651628406,9448719644,146868322055, 2376666773040,41077757951000,762599081332176, 14918668387075449,305774990501285940, 6602482711971622210,149921553418087172260, 3557552268845721893131] |