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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 35 |
| 5 | 218 |
| 6 | 1619 |
| 7 | 13973 |
| 8 | 137216 |
| 9 | 1508981 |
| 10 | 18360015 |
| 11 | 244770120 |
| 12 | 3547043469 |
| 13 | 55499654941 |
| 14 | 932309976082 |
| 15 | 16732137304363 |
| 16 | 319458645821311 |
| 17 | 6464376124430434 |
| 18 | 138181652330967287 |
| 19 | 3111035191655067585 |
[1,1,2,7,35,218,1619,13973,137216,1508981, 18360015,244770120,3547043469,55499654941, 932309976082,16732137304363,319458645821311, 6464376124430434,138181652330967287, 3111035191655067585] |