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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 6 |
| 6 | 17 |
| 7 | 42 |
| 8 | 120 |
| 9 | 330 |
| 10 | 962 |
| 11 | 2797 |
| 12 | 8334 |
| 13 | 24989 |
| 14 | 75905 |
| 15 | 232142 |
| 16 | 715830 |
| 17 | 2220473 |
| 18 | 6928411 |
| 19 | 21723883 |
| 20 | 68424327 |
| 21 | 216376757 |
| 22 | 686742855 |
| 23 | 2186771571 |
| 24 | 6984248840 |
| 25 | 22368127861 |
| 26 | 71818903891 |
| 27 | 231132440916 |
| 28 | 745454242656 |
| 29 | 2409080380316 |
| 30 | 7799945417349 |
[1,1,1,3,6,17,42,120,330,962,2797,8334,24989, 75905,232142,715830,2220473,6928411,21723883, 68424327,216376757,686742855,2186771571, 6984248840,22368127861,71818903891,231132440916, 745454242656,2409080380316,7799945417349] |