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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 32 |
| 4 | 168 |
| 5 | 892 |
| 6 | 4964 |
| 7 | 27854 |
| 8 | 156920 |
| 9 | 891684 |
| 10 | 5095360 |
| 11 | 29236016 |
| 12 | 168361392 |
| 13 | 972601784 |
| 14 | 5633548460 |
| 15 | 32706291872 |
| 16 | 190266981972 |
| 17 | 1108856802378 |
| 18 | 6472638961608 |
| 19 | 37836350087956 |
| 20 | 221461180199752 |
| 21 | 1297757839607606 |
[1,6,32,168,892,4964,27854,156920,891684,5095360, 29236016,168361392,972601784,5633548460, 32706291872,190266981972,1108856802378, 6472638961608,37836350087956,221461180199752, 1297757839607606] |