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| n | a(n) |
|---|---|
| 1 | 672 |
| 2 | 2184 |
| 3 | 6048 |
| 4 | 21048 |
| 5 | 64320 |
| 6 | 233016 |
| 7 | 760608 |
| 8 | 2827992 |
| 9 | 9650112 |
| 10 | 36532344 |
| 11 | 128569248 |
| 12 | 493143768 |
| 13 | 1774812480 |
| 14 | 6874544376 |
| 15 | 25161581088 |
| 16 | 98188573272 |
| 17 | 364094768832 |
| 18 | 1428934093944 |
| 19 | 5353358809248 |
| 20 | 21102161187288 |
| 21 | 79707896139840 |
[672,2184,6048,21048,64320,233016,760608,2827992, 9650112,36532344,128569248,493143768,1774812480, 6874544376,25161581088,98188573272,364094768832, 1428934093944,5353358809248,21102161187288, 79707896139840] |