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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 31 |
| 6 | 112 |
| 7 | 422 |
| 8 | 1635 |
| 9 | 6473 |
| 10 | 26059 |
| 11 | 106327 |
| 12 | 438633 |
| 13 | 1826139 |
| 14 | 7661696 |
| 15 | 32358548 |
| 16 | 137447482 |
| 17 | 586747512 |
| 18 | 2515770639 |
| 19 | 10828744149 |
| 20 | 46772289354 |
| 21 | 202649880510 |
| 22 | 880475437710 |
| 23 | 3835178089380 |
| 24 | 16743665584620 |
[0,1,1,3,9,31,112,422,1635,6473,26059,106327, 438633,1826139,7661696,32358548,137447482, 586747512,2515770639,10828744149,46772289354, 202649880510,880475437710,3835178089380, 16743665584620] |