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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 10 |
| 3 | 64 |
| 4 | 462 |
| 5 | 3584 |
| 6 | 29172 |
| 7 | 245760 |
| 8 | 2124694 |
| 9 | 18743296 |
| 10 | 168043980 |
| 11 | 1526726656 |
| 12 | 14025209100 |
| 13 | 130056978432 |
| 14 | 1215785268840 |
| 15 | 11445014102016 |
| 16 | 108401560073190 |
| 17 | 1032295389593600 |
| 18 | 9877854438949980 |
| 19 | 94927710773575680 |
[1,2,10,64,462,3584,29172,245760,2124694,18743296, 168043980,1526726656,14025209100,130056978432, 1215785268840,11445014102016,108401560073190, 1032295389593600,9877854438949980, 94927710773575680] |