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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 2520 |
| 8 | 8400 |
| 9 | 28728 |
| 10 | 103050 |
| 11 | 390555 |
| 12 | 1566813 |
| 13 | 5994636 |
| 14 | 22318676 |
| 15 | 82337580 |
| 16 | 304360184 |
| 17 | 1134352752 |
| 18 | 4275368704 |
| 19 | 16107425628 |
| 20 | 60453074344 |
| 21 | 226179710040 |
| 22 | 845165016029 |
| 23 | 3159696003981 |
| 24 | 11832636916230 |
| 25 | 44346582492034 |
| 26 | 166184942954284 |
[1,1,2,6,24,120,720,2520,8400,28728,103050,390555, 1566813,5994636,22318676,82337580,304360184, 1134352752,4275368704,16107425628,60453074344, 226179710040,845165016029,3159696003981, 11832636916230,44346582492034,166184942954284] |