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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 74 |
| 6 | 259 |
| 7 | 905 |
| 8 | 3163 |
| 9 | 11058 |
| 10 | 38664 |
| 11 | 135193 |
| 12 | 472724 |
| 13 | 1652965 |
| 14 | 5779907 |
| 15 | 20210571 |
| 16 | 70670238 |
| 17 | 247112450 |
| 18 | 864077593 |
| 19 | 3021418466 |
| 20 | 10564988371 |
| 21 | 36942575637 |
| 22 | 129177037563 |
| 23 | 451693114846 |
| 24 | 1579434503132 |
| 25 | 5522805791005 |
| 26 | 19311585094940 |
| 27 | 67526784937389 |
| 28 | 236120787686511 |
[1,1,2,6,21,74,259,905,3163,11058,38664,135193, 472724,1652965,5779907,20210571,70670238, 247112450,864077593,3021418466,10564988371, 36942575637,129177037563,451693114846, 1579434503132,5522805791005,19311585094940, 67526784937389,236120787686511] |