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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 5 |
| 5 | 11 |
| 6 | 34 |
| 7 | 90 |
| 8 | 300 |
| 9 | 875 |
| 10 | 3038 |
| 11 | 9408 |
| 12 | 33516 |
| 13 | 108108 |
| 14 | 392040 |
| 15 | 1302444 |
| 16 | 4785066 |
| 17 | 16256955 |
| 18 | 60324550 |
| 19 | 208579800 |
| 20 | 780088452 |
| 21 | 2735682092 |
| 22 | 10296854984 |
| 23 | 36532677272 |
| 24 | 138231751840 |
| 25 | 495241833996 |
| 26 | 1882201158264 |
| 27 | 6799413051200 |
| 28 | 25939319270000 |
| 29 | 94374970110000 |
[1,1,2,5,11,34,90,300,875,3038,9408,33516,108108, 392040,1302444,4785066,16256955,60324550, 208579800,780088452,2735682092,10296854984, 36532677272,138231751840,495241833996, 1882201158264,6799413051200,25939319270000, 94374970110000] |