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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 12 |
| 6 | 50 |
| 7 | 210 |
| 8 | 861 |
| 9 | 3416 |
| 10 | 13140 |
| 11 | 49230 |
| 12 | 180455 |
| 13 | 649572 |
| 14 | 2302950 |
| 15 | 8060234 |
| 16 | 27900705 |
| 17 | 95659440 |
| 18 | 325241960 |
| 19 | 1097691462 |
| 20 | 3680494731 |
| 21 | 12268315580 |
| 22 | 40679151450 |
| 23 | 134241199554 |
| 24 | 441078226853 |
| 25 | 1443528742152 |
| 26 | 4707158941500 |
[0,0,1,3,12,50,210,861,3416,13140,49230,180455, 649572,2302950,8060234,27900705,95659440, 325241960,1097691462,3680494731,12268315580, 40679151450,134241199554,441078226853, 1443528742152,4707158941500] |