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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 13 |
| 4 | 99 |
| 5 | 833 |
| 6 | 6755 |
| 7 | 55546 |
| 8 | 454787 |
| 9 | 3731468 |
| 10 | 30604579 |
| 11 | 251081964 |
| 12 | 2059627509 |
| 13 | 16896121515 |
| 14 | 138603472792 |
| 15 | 1137015260752 |
| 16 | 9327306512795 |
| 17 | 76515112946927 |
| 18 | 627679210593852 |
| 19 | 5149066137888295 |
| 20 | 42239532621052491 |
| 21 | 346505218246823715 |
[1,1,13,99,833,6755,55546,454787,3731468,30604579, 251081964,2059627509,16896121515,138603472792, 1137015260752,9327306512795,76515112946927, 627679210593852,5149066137888295, 42239532621052491,346505218246823715] |