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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 81 |
| 6 | 346 |
| 7 | 1630 |
| 8 | 8350 |
| 9 | 45958 |
| 10 | 269815 |
| 11 | 1681285 |
| 12 | 11071336 |
| 13 | 76743040 |
| 14 | 558062437 |
| 15 | 4244853573 |
| 16 | 33687390663 |
| 17 | 278296576327 |
| 18 | 2388351295760 |
| 19 | 21254019548162 |
| 20 | 195801111412320 |
| 21 | 1864508416302520 |
| 22 | 18326903140310011 |
| 23 | 185711672802101781 |
| 24 | 1937795878138303715 |
[1,1,2,6,21,81,346,1630,8350,45958,269815,1681285, 11071336,76743040,558062437,4244853573, 33687390663,278296576327,2388351295760, 21254019548162,195801111412320,1864508416302520, 18326903140310011,185711672802101781, 1937795878138303715] |