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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 15 |
| 6 | 46 |
| 7 | 132 |
| 8 | 432 |
| 9 | 1384 |
| 10 | 4735 |
| 11 | 16158 |
| 12 | 56766 |
| 13 | 200473 |
| 14 | 718012 |
| 15 | 2587000 |
| 16 | 9398080 |
| 17 | 34324173 |
| 18 | 126067124 |
| 19 | 465093570 |
| 20 | 1723171550 |
| 21 | 6407924165 |
| 22 | 23910560070 |
| 23 | 89494164972 |
| 24 | 335913861648 |
| 25 | 1264107416450 |
| 26 | 4768452532025 |
[1,1,1,2,6,15,46,132,432,1384,4735,16158,56766, 200473,718012,2587000,9398080,34324173,126067124, 465093570,1723171550,6407924165,23910560070, 89494164972,335913861648,1264107416450, 4768452532025] |