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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 20 |
| 4 | 84 |
| 5 | 174 |
| 6 | 840 |
| 7 | 1352 |
| 8 | 6120 |
| 9 | 12805 |
| 10 | 42804 |
| 11 | 68892 |
| 12 | 388080 |
| 13 | 468454 |
| 14 | 1938768 |
| 15 | 4680600 |
| 16 | 14595792 |
| 17 | 20460402 |
| 18 | 107024190 |
| 19 | 132502180 |
| 20 | 671765976 |
| 21 | 1235646880 |
| 22 | 3356004888 |
| 23 | 5401408344 |
| 24 | 32600383200 |
| 25 | 40663881751 |
| 26 | 133006270404 |
| 27 | 305814801800 |
[1,6,20,84,174,840,1352,6120,12805,42804,68892, 388080,468454,1938768,4680600,14595792,20460402, 107024190,132502180,671765976,1235646880, 3356004888,5401408344,32600383200,40663881751, 133006270404,305814801800] |