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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 2 |
| 5 | 10 |
| 6 | 0 |
| 7 | 0 |
| 8 | 0 |
| 9 | 0 |
| 10 | 48 |
| 11 | 152 |
| 12 | 472 |
| 13 | 2696 |
| 14 | 12320 |
| 15 | 74436 |
| 16 | 429620 |
| 17 | 2515116 |
| 18 | 16122496 |
| 19 | 113016608 |
| 20 | 843492920 |
| 21 | 6575649316 |
| 22 | 54694203188 |
[1,0,0,2,10,0,0,0,0,48,152,472,2696,12320,74436, 429620,2515116,16122496,113016608,843492920, 6575649316,54694203188] |