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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 40 |
| 5 | 176 |
| 6 | 672 |
| 7 | 2752 |
| 8 | 10880 |
| 9 | 43776 |
| 10 | 174592 |
| 11 | 699392 |
| 12 | 2795520 |
| 13 | 11186176 |
| 14 | 44736512 |
| 15 | 178962432 |
| 16 | 715816960 |
| 17 | 2863333376 |
| 18 | 11453202432 |
| 19 | 45813071872 |
| 20 | 183251763200 |
| 21 | 733008101376 |
| 22 | 2932030308352 |
| 23 | 11728125427712 |
[0,1,2,12,40,176,672,2752,10880,43776,174592, 699392,2795520,11186176,44736512,178962432, 715816960,2863333376,11453202432,45813071872, 183251763200,733008101376,2932030308352, 11728125427712] |