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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 28 |
| 5 | 145 |
| 6 | 880 |
| 7 | 6221 |
| 8 | 50048 |
| 9 | 452097 |
| 10 | 4531440 |
| 11 | 49919461 |
| 12 | 599595192 |
| 13 | 7799387921 |
| 14 | 109232872424 |
| 15 | 1638888843541 |
| 16 | 26226252579296 |
| 17 | 445889920626817 |
| 18 | 8026518496420896 |
| 19 | 152509898418037765 |
| 20 | 3050274960962524520 |
| 21 | 64056803495548131665 |
| 22 | 1409264093116606297080 |
[1,1,2,7,28,145,880,6221,50048,452097,4531440, 49919461,599595192,7799387921,109232872424, 1638888843541,26226252579296,445889920626817, 8026518496420896,152509898418037765, 3050274960962524520,64056803495548131665, 1409264093116606297080] |