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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 8 |
| 4 | 16 |
| 5 | 72 |
| 6 | 240 |
| 7 | 736 |
| 8 | 2352 |
| 9 | 7128 |
| 10 | 21424 |
| 11 | 63768 |
| 12 | 187424 |
| 13 | 547136 |
| 14 | 1586016 |
| 15 | 4570280 |
| 16 | 13105488 |
| 17 | 37414632 |
| 18 | 106404944 |
| 19 | 301580704 |
| 20 | 852159120 |
| 21 | 2401326712 |
| 22 | 6750087408 |
| 23 | 18931901880 |
| 24 | 52989773184 |
| 25 | 148039566336 |
| 26 | 412873929408 |
| 27 | 1149659579720 |
[0,0,8,16,72,240,736,2352,7128,21424,63768,187424, 547136,1586016,4570280,13105488,37414632, 106404944,301580704,852159120,2401326712, 6750087408,18931901880,52989773184,148039566336, 412873929408,1149659579720] |