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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 14 |
| 5 | 65 |
| 6 | 370 |
| 7 | 2496 |
| 8 | 19339 |
| 9 | 169215 |
| 10 | 1649844 |
| 11 | 17735823 |
| 12 | 208395916 |
| 13 | 2657047924 |
| 14 | 36534408954 |
| 15 | 538882532061 |
| 16 | 8487399879955 |
| 17 | 142163947989233 |
| 18 | 2523410076808877 |
| 19 | 47313938940166439 |
| 20 | 934450294068287158 |
[1,1,2,4,14,65,370,2496,19339,169215,1649844, 17735823,208395916,2657047924,36534408954, 538882532061,8487399879955,142163947989233, 2523410076808877,47313938940166439, 934450294068287158] |