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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 15 |
| 3 | 124 |
| 4 | 1167 |
| 5 | 11772 |
| 6 | 124561 |
| 7 | 1363964 |
| 8 | 15326826 |
| 9 | 175739698 |
| 10 | 2047974619 |
| 11 | 24185317182 |
| 12 | 288801732423 |
| 13 | 3481242975808 |
| 14 | 42303574158234 |
| 15 | 517683469595912 |
| 16 | 6374096109874427 |
| 17 | 78909384182870688 |
| 18 | 981600144994348111 |
| 19 | 12263583888826309544 |
| 20 | 153812133876403777005 |
[1,2,15,124,1167,11772,124561,1363964,15326826, 175739698,2047974619,24185317182,288801732423, 3481242975808,42303574158234,517683469595912, 6374096109874427,78909384182870688, 981600144994348111,12263583888826309544, 153812133876403777005] |