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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 5 |
| 6 | 12 |
| 7 | 42 |
| 8 | 110 |
| 9 | 462 |
| 10 | 1274 |
| 11 | 6006 |
| 12 | 17136 |
| 13 | 87516 |
| 14 | 255816 |
| 15 | 1385670 |
| 16 | 4124406 |
| 17 | 23371634 |
| 18 | 70549050 |
| 19 | 414315330 |
| 20 | 1264752060 |
| 21 | 7646001090 |
| 22 | 23555382240 |
| 23 | 145862174640 |
| 24 | 452806924752 |
| 25 | 2861142656400 |
| 26 | 8939481277552 |
| 27 | 57468093927120 |
[1,1,1,2,5,12,42,110,462,1274,6006,17136,87516, 255816,1385670,4124406,23371634,70549050, 414315330,1264752060,7646001090,23555382240, 145862174640,452806924752,2861142656400, 8939481277552,57468093927120] |