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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 36 |
| 5 | 330 |
| 6 | 4092 |
| 7 | 63308 |
| 8 | 1165952 |
| 9 | 24802704 |
| 10 | 596862420 |
| 11 | 16003332092 |
| 12 | 472588688880 |
| 13 | 15231153085304 |
| 14 | 531801227022912 |
| 15 | 19992702649780800 |
| 16 | 805099660439308672 |
| 17 | 34574148236596003008 |
| 18 | 1577229602738525889984 |
| 19 | 76172611622917782581040 |
| 20 | 3882814240467405224924960 |
| 21 | 208333046141920439476582608 |
| 22 | 11737307286279509352537747760 |
[1,2,6,36,330,4092,63308,1165952,24802704, 596862420,16003332092,472588688880,15231153085304, 531801227022912,19992702649780800, 805099660439308672,34574148236596003008, 1577229602738525889984,76172611622917782581040, 3882814240467405224924960, 208333046141920439476582608, 11737307286279509352537747760] |