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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 6 |
| 3 | 15 |
| 4 | 30 |
| 5 | 70 |
| 6 | 140 |
| 7 | 315 |
| 8 | 630 |
| 9 | 1386 |
| 10 | 2772 |
| 11 | 6006 |
| 12 | 12012 |
| 13 | 25740 |
| 14 | 51480 |
| 15 | 109395 |
| 16 | 218790 |
| 17 | 461890 |
| 18 | 923780 |
| 19 | 1939938 |
| 20 | 3879876 |
| 21 | 8112468 |
| 22 | 16224936 |
| 23 | 33801950 |
| 24 | 67603900 |
| 25 | 140408100 |
| 26 | 280816200 |
| 27 | 581690700 |
| 28 | 1163381400 |
| 29 | 2404321560 |
| 30 | 4808643120 |
| 31 | 9917826435 |
| 32 | 19835652870 |
[1,3,6,15,30,70,140,315,630,1386,2772,6006,12012, 25740,51480,109395,218790,461890,923780,1939938, 3879876,8112468,16224936,33801950,67603900, 140408100,280816200,581690700,1163381400, 2404321560,4808643120,9917826435,19835652870] |