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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 71 |
| 5 | 441 |
| 6 | 2955 |
| 7 | 20805 |
| 8 | 151695 |
| 9 | 1135345 |
| 10 | 8671763 |
| 11 | 67320573 |
| 12 | 529626839 |
| 13 | 4213228969 |
| 14 | 33833367963 |
| 15 | 273892683573 |
| 16 | 2232832964895 |
| 17 | 18314495896545 |
| 18 | 151037687326755 |
| 19 | 1251606057754605 |
| 20 | 10416531069771111 |
| 21 | 87029307323766681 |
[1,1,3,13,71,441,2955,20805,151695,1135345, 8671763,67320573,529626839,4213228969,33833367963, 273892683573,2232832964895,18314495896545, 151037687326755,1251606057754605, 10416531069771111,87029307323766681] |