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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 20 |
| 5 | 91 |
| 6 | 362 |
| 7 | 2227 |
| 8 | 11720 |
| 9 | 92491 |
| 10 | 608222 |
| 11 | 5866147 |
| 12 | 46290620 |
| 13 | 527635291 |
| 14 | 4857587282 |
| 15 | 63886537267 |
| 16 | 672183848720 |
| 17 | 10019232896491 |
| 18 | 118594819341542 |
| 19 | 1975680877259587 |
| 20 | 25983971598078020 |
| 21 | 478434297205284091 |
| 22 | 6921555837554655002 |
| 23 | 139581878985127217107 |
[0,1,2,7,20,91,362,2227,11720,92491,608222, 5866147,46290620,527635291,4857587282,63886537267, 672183848720,10019232896491,118594819341542, 1975680877259587,25983971598078020, 478434297205284091,6921555837554655002, 139581878985127217107] |