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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 26 |
| 4 | 144 |
| 5 | 962 |
| 6 | 7536 |
| 7 | 67706 |
| 8 | 685824 |
| 9 | 7730882 |
| 10 | 95970816 |
| 11 | 1300815386 |
| 12 | 19113775104 |
| 13 | 302616787202 |
| 14 | 5135568746496 |
| 15 | 92996021795066 |
| 16 | 1789758460329984 |
| 17 | 36479831022049922 |
| 18 | 785020114093080576 |
| 19 | 17785273588395966746 |
[1,2,6,26,144,962,7536,67706,685824,7730882, 95970816,1300815386,19113775104,302616787202, 5135568746496,92996021795066,1789758460329984, 36479831022049922,785020114093080576, 17785273588395966746] |