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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 80 |
| 6 | 128 |
| 7 | -2940 |
| 8 | -63072 |
| 9 | -932088 |
| 10 | -11628648 |
| 11 | -114829968 |
| 12 | -417677856 |
| 13 | 21173151792 |
| 14 | 869103962400 |
| 15 | 23125766258208 |
| 16 | 492858262277472 |
| 17 | 7960636847682816 |
| 18 | 46152793911618432 |
| 19 | -3484964629275707328 |
| 20 | -212667378331722666240 |
[1,2,6,22,80,128,-2940,-63072,-932088,-11628648, -114829968,-417677856,21173151792,869103962400, 23125766258208,492858262277472,7960636847682816, 46152793911618432,-3484964629275707328, -212667378331722666240] |