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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 55 |
| 3 | 472 |
| 4 | 4300 |
| 5 | 40861 |
| 6 | 400567 |
| 7 | 4021720 |
| 8 | 41147398 |
| 9 | 427470430 |
| 10 | 4497253054 |
| 11 | 47817544348 |
| 12 | 513029453530 |
| 13 | 5547155801065 |
| 14 | 60385754935495 |
| 15 | 661267785740080 |
| 16 | 7279524885630310 |
| 17 | 80512572260496610 |
| 18 | 894231158402339410 |
[1,7,55,472,4300,40861,400567,4021720,41147398, 427470430,4497253054,47817544348,513029453530, 5547155801065,60385754935495,661267785740080, 7279524885630310,80512572260496610, 894231158402339410] |