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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 11 |
| 4 | 60 |
| 5 | 384 |
| 6 | 3062 |
| 7 | 27838 |
| 8 | 293416 |
| 9 | 3447768 |
| 10 | 45277392 |
| 11 | 651587760 |
| 12 | 10254900048 |
| 13 | 174557518992 |
| 14 | 3203361670896 |
| 15 | 62938642659504 |
| 16 | 1319693558377728 |
| 17 | 29390794198726656 |
| 18 | 693223221342879360 |
| 19 | 17256288944072200320 |
| 20 | 452215395177034040064 |
[1,1,3,11,60,384,3062,27838,293416,3447768, 45277392,651587760,10254900048,174557518992, 3203361670896,62938642659504,1319693558377728, 29390794198726656,693223221342879360, 17256288944072200320,452215395177034040064] |