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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 116 |
| 6 | 628 |
| 7 | 3636 |
| 8 | 21956 |
| 9 | 136428 |
| 10 | 865700 |
| 11 | 5583580 |
| 12 | 36490740 |
| 13 | 241105516 |
| 14 | 1607891780 |
| 15 | 10808452348 |
| 16 | 73159943124 |
| 17 | 498215170508 |
| 18 | 3411058716964 |
| 19 | 23465785541468 |
| 20 | 162121010290996 |
| 21 | 1124393414877996 |
| 22 | 7825541946451972 |
| 23 | 54637557152397884 |
| 24 | 382586828736801940 |
| 25 | 2686126809776641932 |
[1,1,2,6,24,116,628,3636,21956,136428,865700, 5583580,36490740,241105516,1607891780,10808452348, 73159943124,498215170508,3411058716964, 23465785541468,162121010290996,1124393414877996, 7825541946451972,54637557152397884, 382586828736801940,2686126809776641932] |