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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 25 |
| 6 | 108 |
| 7 | 513 |
| 8 | 2690 |
| 9 | 15230 |
| 10 | 92361 |
| 11 | 594669 |
| 12 | 4040283 |
| 13 | 28817783 |
| 14 | 214898429 |
| 15 | 1669663193 |
| 16 | 13476692136 |
| 17 | 112722792293 |
| 18 | 974931812942 |
| 19 | 8702563358405 |
| 20 | 80039193725904 |
| 21 | 757342429877879 |
| 22 | 7362651015248190 |
| 23 | 73451961108974776 |
| 24 | 751144076656119144 |
| 25 | 7866092802569673370 |
[1,1,1,2,7,25,108,513,2690,15230,92361,594669, 4040283,28817783,214898429,1669663193,13476692136, 112722792293,974931812942,8702563358405, 80039193725904,757342429877879,7362651015248190, 73451961108974776,751144076656119144, 7866092802569673370] |