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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 64 |
| 5 | 630 |
| 6 | 8030 |
| 7 | 126247 |
| 8 | 2371612 |
| 9 | 52026293 |
| 10 | 1309661828 |
| 11 | 37318672196 |
| 12 | 1190672836246 |
| 13 | 42159850045181 |
| 14 | 1644546319080848 |
| 15 | 70233352188006641 |
| 16 | 3266637689293293616 |
| 17 | 164720219739258021686 |
| 18 | 8969422973088951968070 |
| 19 | 525585300443124229026511 |
| 20 | 33039986976855724686082476 |
[1,1,2,9,64,630,8030,126247,2371612,52026293, 1309661828,37318672196,1190672836246, 42159850045181,1644546319080848,70233352188006641, 3266637689293293616,164720219739258021686, 8969422973088951968070,525585300443124229026511, 33039986976855724686082476] |