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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 8 |
| 2 | 48 |
| 3 | 270 |
| 4 | 1392 |
| 5 | 6862 |
| 6 | 32440 |
| 7 | 149114 |
| 8 | 674344 |
| 9 | 3003292 |
| 10 | 13234674 |
| 11 | 57809228 |
| 12 | 250594424 |
| 13 | 1079480960 |
| 14 | 4624303560 |
| 15 | 19720668918 |
| 16 | 83744226026 |
| 17 | 354354250476 |
| 18 | 1494620712320 |
| 19 | 6286217598392 |
[2,8,48,270,1392,6862,32440,149114,674344,3003292, 13234674,57809228,250594424,1079480960,4624303560, 19720668918,83744226026,354354250476, 1494620712320,6286217598392] |