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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 38 |
| 5 | 286 |
| 6 | 2756 |
| 7 | 32299 |
| 8 | 444998 |
| 9 | 7038898 |
| 10 | 125620652 |
| 11 | 2495811814 |
| 12 | 54618201884 |
| 13 | 1305184303996 |
| 14 | 33812846036552 |
| 15 | 943878836768947 |
| 16 | 28242424937855558 |
| 17 | 901709392642750186 |
| 18 | 30597227032818965276 |
| 19 | 1099566630423067201234 |
| 20 | 41718229482624755005748 |
[1,1,2,7,38,286,2756,32299,444998,7038898, 125620652,2495811814,54618201884,1305184303996, 33812846036552,943878836768947,28242424937855558, 901709392642750186,30597227032818965276, 1099566630423067201234,41718229482624755005748] |