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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 52 |
| 3 | 518 |
| 4 | 5480 |
| 5 | 59883 |
| 6 | 667788 |
| 7 | 7551472 |
| 8 | 86268736 |
| 9 | 993247305 |
| 10 | 11506149009 |
| 11 | 133956128894 |
| 12 | 1565956239176 |
| 13 | 18369435931103 |
| 14 | 216117213446306 |
| 15 | 2549084979617775 |
| 16 | 30132752342280996 |
| 17 | 356891926172012205 |
| 18 | 4234302321795870255 |
| 19 | 50314550016599999131 |
| 20 | 598692305693300128869 |
[1,6,52,518,5480,59883,667788,7551472,86268736, 993247305,11506149009,133956128894,1565956239176, 18369435931103,216117213446306,2549084979617775, 30132752342280996,356891926172012205, 4234302321795870255,50314550016599999131, 598692305693300128869] |