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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 2 |
| 3 | 55 |
| 4 | 208 |
| 5 | 2778 |
| 6 | 17050 |
| 7 | 166531 |
| 8 | 1221727 |
| 9 | 10652903 |
| 10 | 83558723 |
| 11 | 698912193 |
| 12 | 5620874008 |
| 13 | 46297856418 |
| 14 | 375826633534 |
| 15 | 3078013187839 |
| 16 | 25072750273992 |
| 17 | 204911552403250 |
| 18 | 1671311190316246 |
| 19 | 13648365689804011 |
| 20 | 111372868203567131 |
[2,2,55,208,2778,17050,166531,1221727,10652903, 83558723,698912193,5620874008,46297856418, 375826633534,3078013187839,25072750273992, 204911552403250,1671311190316246, 13648365689804011,111372868203567131] |