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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 23 |
| 4 | 91 |
| 5 | 365 |
| 6 | 1529 |
| 7 | 6552 |
| 8 | 28329 |
| 9 | 123993 |
| 10 | 548439 |
| 11 | 2441621 |
| 12 | 10936491 |
| 13 | 49261695 |
| 14 | 222834197 |
| 15 | 1011830689 |
| 16 | 4610728789 |
| 17 | 21071941581 |
| 18 | 96554920713 |
| 19 | 443512797674 |
| 20 | 2041601345727 |
| 21 | 9416130159996 |
| 22 | 43506635862108 |
| 23 | 201349038433485 |
| 24 | 933234334342715 |
| 25 | 4331475468258564 |
| 26 | 20129858878208957 |
| 27 | 93661790304961226 |
[1,2,6,23,91,365,1529,6552,28329,123993,548439, 2441621,10936491,49261695,222834197,1011830689, 4610728789,21071941581,96554920713,443512797674, 2041601345727,9416130159996,43506635862108, 201349038433485,933234334342715,4331475468258564, 20129858878208957,93661790304961226] |