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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 24 |
| 4 | 98 |
| 5 | 412 |
| 6 | 1840 |
| 7 | 8154 |
| 8 | 37224 |
| 9 | 171160 |
| 10 | 793154 |
| 11 | 3716730 |
| 12 | 17465560 |
| 13 | 82664746 |
| 14 | 392713914 |
| 15 | 1872141724 |
| 16 | 8959486334 |
| 17 | 42973967858 |
| 18 | 206712819136 |
| 19 | 996416355570 |
| 20 | 4812329849512 |
| 21 | 23285606526834 |
| 22 | 112842422049906 |
| 23 | 547665328751596 |
| 24 | 2661489800389408 |
| 25 | 12949604740884364 |
| 26 | 63078260567268032 |
| 27 | 307567027977622324 |
[1,2,6,24,98,412,1840,8154,37224,171160,793154, 3716730,17465560,82664746,392713914,1872141724, 8959486334,42973967858,206712819136,996416355570, 4812329849512,23285606526834,112842422049906, 547665328751596,2661489800389408, 12949604740884364,63078260567268032, 307567027977622324] |