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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 3 |
| 4 | 10 |
| 5 | 54 |
| 6 | 222 |
| 7 | 1107 |
| 8 | 5346 |
| 9 | 27399 |
| 10 | 142770 |
| 11 | 764967 |
| 12 | 4170672 |
| 13 | 23140813 |
| 14 | 130189302 |
| 15 | 741650172 |
| 16 | 4270501218 |
| 17 | 24825326196 |
| 18 | 145534796520 |
| 19 | 859627488963 |
| 20 | 5112003992610 |
| 21 | 30586307195304 |
| 22 | 184023393204654 |
| 23 | 1112800162657899 |
[1,1,0,3,10,54,222,1107,5346,27399,142770,764967, 4170672,23140813,130189302,741650172,4270501218, 24825326196,145534796520,859627488963, 5112003992610,30586307195304,184023393204654, 1112800162657899] |