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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 2 |
| 7 | 5 |
| 8 | 15 |
| 9 | 52 |
| 10 | 204 |
| 11 | 902 |
| 12 | 4532 |
| 13 | 26196 |
| 14 | 175320 |
| 15 | 1351296 |
| 16 | 11819348 |
| 17 | 115309534 |
| 18 | 1236465988 |
| 19 | 14419850138 |
| 20 | 181652022376 |
| 21 | 2462053028798 |
| 22 | 35834756184146 |
| 23 | 559816444117400 |
| 24 | 9389648056139010 |
| 25 | 169166236946379128 |
| 26 | 3273760080403458226 |
| 27 | 67994123544008546820 |
[1,1,1,1,1,1,2,5,15,52,204,902,4532,26196,175320, 1351296,11819348,115309534,1236465988,14419850138, 181652022376,2462053028798,35834756184146, 559816444117400,9389648056139010, 169166236946379128,3273760080403458226, 67994123544008546820] |