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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 2 |
| 6 | 4 |
| 7 | 22 |
| 8 | 124 |
| 9 | 816 |
| 10 | 6112 |
| 11 | 51642 |
| 12 | 485604 |
| 13 | 5034606 |
| 14 | 57080204 |
| 15 | 702766384 |
| 16 | 9339630016 |
| 17 | 133281949954 |
| 18 | 2033044422948 |
| 19 | 33014191980502 |
| 20 | 568686463073484 |
| 21 | 10357838456504880 |
[0,0,0,0,2,4,22,124,816,6112,51642,485604,5034606, 57080204,702766384,9339630016,133281949954, 2033044422948,33014191980502,568686463073484, 10357838456504880] |