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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 4 |
| 4 | 15 |
| 5 | 21 |
| 6 | 84 |
| 7 | 120 |
| 8 | 495 |
| 9 | 715 |
| 10 | 3003 |
| 11 | 4368 |
| 12 | 18564 |
| 13 | 27132 |
| 14 | 116280 |
| 15 | 170544 |
| 16 | 735471 |
| 17 | 1081575 |
| 18 | 4686825 |
| 19 | 6906900 |
| 20 | 30045015 |
| 21 | 44352165 |
| 22 | 193536720 |
| 23 | 286097760 |
| 24 | 1251677700 |
| 25 | 1852482996 |
| 26 | 8122425444 |
| 27 | 12033222880 |
| 28 | 52860229080 |
| 29 | 78378960360 |
[1,1,3,4,15,21,84,120,495,715,3003,4368,18564, 27132,116280,170544,735471,1081575,4686825, 6906900,30045015,44352165,193536720,286097760, 1251677700,1852482996,8122425444,12033222880, 52860229080,78378960360] |