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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 15 |
| 3 | 144 |
| 4 | 1587 |
| 5 | 18942 |
| 6 | 238301 |
| 7 | 3111788 |
| 8 | 41779164 |
| 9 | 573127760 |
| 10 | 7998164674 |
| 11 | 113189243386 |
| 12 | 1620583793262 |
| 13 | 23431706243230 |
| 14 | 341654376602948 |
| 15 | 5017986762425680 |
| 16 | 74170837061591036 |
| 17 | 1102479579201183898 |
| 18 | 16469074050937364044 |
| 19 | 247115476148847822586 |
[1,2,15,144,1587,18942,238301,3111788,41779164, 573127760,7998164674,113189243386,1620583793262, 23431706243230,341654376602948,5017986762425680, 74170837061591036,1102479579201183898, 16469074050937364044,247115476148847822586] |