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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 119 |
| 6 | 694 |
| 7 | 4578 |
| 8 | 33184 |
| 9 | 258757 |
| 10 | 2136978 |
| 11 | 18478134 |
| 12 | 165857600 |
| 13 | 1535336290 |
| 14 | 14584260700 |
| 15 | 141603589300 |
| 16 | 1400942032152 |
| 17 | 14087464765300 |
| 18 | 143689133196008 |
| 19 | 1484090443264936 |
| 20 | 15499968503875136 |
| 21 | 163501005435759505 |
| 22 | 1740170514634463426 |
| 23 | 18671118911254798454 |
[1,1,2,6,24,119,694,4578,33184,258757,2136978, 18478134,165857600,1535336290,14584260700, 141603589300,1400942032152,14087464765300, 143689133196008,1484090443264936, 15499968503875136,163501005435759505, 1740170514634463426,18671118911254798454] |