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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 6 |
| 3 | 22 |
| 4 | 224 |
| 5 | 2138 |
| 6 | 25732 |
| 7 | 351846 |
| 8 | 5458224 |
| 9 | 94441042 |
| 10 | 1803255404 |
| 11 | 37652268014 |
| 12 | 853321021192 |
| 13 | 20858236815258 |
| 14 | 546941712302052 |
| 15 | 15313467390967222 |
| 16 | 455933682027961184 |
| 17 | 14383416438784605602 |
| 18 | 479254037890010238172 |
| 19 | 16817855455956128823486 |
| 20 | 619953003446894086537656 |
[1,0,6,22,224,2138,25732,351846,5458224,94441042, 1803255404,37652268014,853321021192, 20858236815258,546941712302052,15313467390967222, 455933682027961184,14383416438784605602, 479254037890010238172,16817855455956128823486, 619953003446894086537656] |