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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 719 |
| 7 | 5022 |
| 8 | 40064 |
| 9 | 359400 |
| 10 | 3580896 |
| 11 | 39233867 |
| 12 | 468818397 |
| 13 | 6067548429 |
| 14 | 84551873634 |
| 15 | 1262188317534 |
| 16 | 20095114167065 |
| 17 | 339883289813330 |
| 18 | 6086154606429378 |
| 19 | 115025120586250896 |
| 20 | 2288119443771888504 |
| 21 | 47787869441095495395 |
| 22 | 1045507132393256095282 |
[1,1,2,6,24,120,719,5022,40064,359400,3580896, 39233867,468818397,6067548429,84551873634, 1262188317534,20095114167065,339883289813330, 6086154606429378,115025120586250896, 2288119443771888504,47787869441095495395, 1045507132393256095282] |