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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 36 |
| 4 | 176 |
| 5 | 920 |
| 6 | 5080 |
| 7 | 29336 |
| 8 | 175752 |
| 9 | 1085496 |
| 10 | 6877240 |
| 11 | 44518520 |
| 12 | 293513784 |
| 13 | 1965904984 |
| 14 | 13348449784 |
| 15 | 91723622936 |
| 16 | 636923476728 |
| 17 | 4463989946072 |
| 18 | 31545992160568 |
| 19 | 224580029779608 |
| 20 | 1609455072125816 |
| 21 | 11603437881340888 |
[1,2,8,36,176,920,5080,29336,175752,1085496, 6877240,44518520,293513784,1965904984,13348449784, 91723622936,636923476728,4463989946072, 31545992160568,224580029779608,1609455072125816, 11603437881340888] |