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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 13 |
| 5 | 40 |
| 6 | 205 |
| 7 | 952 |
| 8 | 4921 |
| 9 | 31168 |
| 10 | 189145 |
| 11 | 1318528 |
| 12 | 9843781 |
| 13 | 74869888 |
| 14 | 632536933 |
| 15 | 5475991552 |
| 16 | 49996774897 |
| 17 | 485393809408 |
| 18 | 4829958877105 |
| 19 | 50858117779456 |
| 20 | 554544498995965 |
| 21 | 6259096187060224 |
| 22 | 73822470722135293 |
| 23 | 894846287081242624 |
| 24 | 11261265009125680681 |
| 25 | 146272258394568687616 |
[1,1,1,4,13,40,205,952,4921,31168,189145,1318528, 9843781,74869888,632536933,5475991552,49996774897, 485393809408,4829958877105,50858117779456, 554544498995965,6259096187060224, 73822470722135293,894846287081242624, 11261265009125680681,146272258394568687616] |