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| n | a(n) |
|---|---|
| -1 | 3 |
| 0 | 8 |
| 1 | 30 |
| 2 | 132 |
| 3 | 612 |
| 4 | 2880 |
| 5 | 13608 |
| 6 | 64368 |
| 7 | 304560 |
| 8 | 1441152 |
| 9 | 6819552 |
| 10 | 32270400 |
| 11 | 152705088 |
| 12 | 722608128 |
| 13 | 3419418240 |
| 14 | 16180860672 |
| 15 | 76568654592 |
| 16 | 362326763520 |
| 17 | 1714548653568 |
| 18 | 8113331340288 |
| 19 | 38392696120320 |
| 20 | 181676188680192 |
[3,8,30,132,612,2880,13608,64368,304560,1441152, 6819552,32270400,152705088,722608128,3419418240, 16180860672,76568654592,362326763520, 1714548653568,8113331340288,38392696120320, 181676188680192] |