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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 9 |
| 3 | 62 |
| 4 | 390 |
| 5 | 2384 |
| 6 | 14680 |
| 7 | 93680 |
| 8 | 635824 |
| 9 | 4697664 |
| 10 | 38442112 |
| 11 | 351331584 |
| 12 | 3582715136 |
| 13 | 40476303360 |
| 14 | 501863078912 |
| 15 | 6767130867712 |
| 16 | 98464775493632 |
| 17 | 1536203429306368 |
| 18 | 25564684461735936 |
| 19 | 451816479967608832 |
| 20 | 8448863295040978944 |
| 21 | 166627401783086415872 |
| 22 | 3455980532191764676608 |
[0,1,9,62,390,2384,14680,93680,635824,4697664, 38442112,351331584,3582715136,40476303360, 501863078912,6767130867712,98464775493632, 1536203429306368,25564684461735936, 451816479967608832,8448863295040978944, 166627401783086415872,3455980532191764676608] |