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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 40 |
| 5 | 200 |
| 6 | 1286 |
| 7 | 9002 |
| 8 | 74712 |
| 9 | 672408 |
| 10 | 6892312 |
| 11 | 75815432 |
| 12 | 925733216 |
| 13 | 12034531808 |
| 14 | 170656068480 |
| 15 | 2559841027200 |
| 16 | 41356302857344 |
| 17 | 703057148574848 |
| 18 | 12752569691858048 |
| 19 | 242298824145302912 |
| 20 | 4875886476833445888 |
| 21 | 102393616013502363648 |
| 22 | 2264106940756915715584 |
[1,1,3,9,40,200,1286,9002,74712,672408,6892312, 75815432,925733216,12034531808,170656068480, 2559841027200,41356302857344,703057148574848, 12752569691858048,242298824145302912, 4875886476833445888,102393616013502363648, 2264106940756915715584] |