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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 719 |
| 7 | 5037 |
| 8 | 40306 |
| 9 | 362802 |
| 10 | 3628296 |
| 11 | 39913080 |
| 12 | 478970641 |
| 13 | 6226733531 |
| 14 | 87175347936 |
| 15 | 1307641346772 |
| 16 | 20922387099240 |
| 17 | 355682119243320 |
| 18 | 6402298503373917 |
| 19 | 121643960874649867 |
| 20 | 2432883613692550316 |
| 21 | 51090627024035616300 |
| 22 | 1123995015882951892680 |
[1,1,2,6,24,120,719,5037,40306,362802,3628296, 39913080,478970641,6226733531,87175347936, 1307641346772,20922387099240,355682119243320, 6402298503373917,121643960874649867, 2432883613692550316,51090627024035616300, 1123995015882951892680] |