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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 12 |
| 4 | 120 |
| 5 | 1160 |
| 6 | 11340 |
| 7 | 113988 |
| 8 | 1185968 |
| 9 | 12802896 |
| 10 | 143475300 |
| 11 | 1668342060 |
| 12 | 20111265768 |
| 13 | 251047344600 |
| 14 | 3241258872124 |
| 15 | 43230289541460 |
| 16 | 594927620980320 |
| 17 | 8438127851537312 |
| 18 | 123214473695309652 |
| 19 | 1850390947982126268 |
[0,0,1,12,120,1160,11340,113988,1185968,12802896, 143475300,1668342060,20111265768,251047344600, 3241258872124,43230289541460,594927620980320, 8438127851537312,123214473695309652, 1850390947982126268] |