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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 12 |
| 3 | 189 |
| 4 | 2808 |
| 5 | 42201 |
| 6 | 632772 |
| 7 | 9492309 |
| 8 | 142382448 |
| 9 | 2135743281 |
| 10 | 32036129532 |
| 11 | 480542002029 |
| 12 | 7208129853288 |
| 13 | 108121948330761 |
| 14 | 1621829223367092 |
| 15 | 24327438355289349 |
| 16 | 364911575314991328 |
| 17 | 5473673629767916641 |
| 18 | 82105104446389609452 |
[0,1,12,189,2808,42201,632772,9492309,142382448, 2135743281,32036129532,480542002029,7208129853288, 108121948330761,1621829223367092, 24327438355289349,364911575314991328, 5473673629767916641,82105104446389609452] |