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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 29 |
| 4 | 312 |
| 5 | 4481 |
| 6 | 80768 |
| 7 | 1754549 |
| 8 | 44647040 |
| 9 | 1303097665 |
| 10 | 42923116032 |
| 11 | 1575332861101 |
| 12 | 63754405679104 |
| 13 | 2820829737123841 |
| 14 | 135469202252333056 |
| 15 | 7018336152909163205 |
| 16 | 390175030207597805568 |
| 17 | 23169468447962190613121 |
| 18 | 1463683656780476860989440 |
| 19 | 98016257612539018485477821 |
[1,1,4,29,312,4481,80768,1754549,44647040, 1303097665,42923116032,1575332861101, 63754405679104,2820829737123841, 135469202252333056,7018336152909163205, 390175030207597805568,23169468447962190613121, 1463683656780476860989440, 98016257612539018485477821] |