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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 4 |
| 3 | 0 |
| 4 | 176 |
| 5 | 0 |
| 6 | 24192 |
| 7 | 0 |
| 8 | 6966528 |
| 9 | 0 |
| 10 | 3459768320 |
| 11 | 0 |
| 12 | 2642804895744 |
| 13 | 0 |
| 14 | 2880385956446208 |
| 15 | 0 |
| 16 | 4248075487709560832 |
| 17 | 0 |
| 18 | 8150896954121845211136 |
| 19 | 0 |
| 20 | 19738484719911211593891840 |
| 21 | 0 |
| 22 | 58891248341123034677673721856 |
| 23 | 0 |
[1,0,4,0,176,0,24192,0,6966528,0,3459768320,0, 2642804895744,0,2880385956446208,0, 4248075487709560832,0,8150896954121845211136,0, 19738484719911211593891840,0, 58891248341123034677673721856,0] |