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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 0 |
| 3 | 8 |
| 4 | 16 |
| 5 | 72 |
| 6 | 240 |
| 7 | 968 |
| 8 | 3696 |
| 9 | 14792 |
| 10 | 58480 |
| 11 | 233928 |
| 12 | 932976 |
| 13 | 3731912 |
| 14 | 14916720 |
| 15 | 59666888 |
| 16 | 238623856 |
| 17 | 954495432 |
| 18 | 3817806960 |
| 19 | 15271227848 |
| 20 | 61084212336 |
| 21 | 244336849352 |
| 22 | 977344601200 |
| 23 | 3909378404808 |
[0,2,0,8,16,72,240,968,3696,14792,58480,233928, 932976,3731912,14916720,59666888,238623856, 954495432,3817806960,15271227848,61084212336, 244336849352,977344601200,3909378404808] |