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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 18 |
| 2 | 378 |
| 3 | 7938 |
| 4 | 166698 |
| 5 | 3500658 |
| 6 | 73513818 |
| 7 | 1543790178 |
| 8 | 32419593738 |
| 9 | 680811468498 |
| 10 | 14297040838458 |
| 11 | 300237857607618 |
| 12 | 6304995009759978 |
| 13 | 132404895204959538 |
| 14 | 2780502799304150298 |
| 15 | 58390558785387156258 |
| 16 | 1226201734493130281418 |
| 17 | 25750236424355735909778 |
[1,18,378,7938,166698,3500658,73513818,1543790178, 32419593738,680811468498,14297040838458, 300237857607618,6304995009759978, 132404895204959538,2780502799304150298, 58390558785387156258,1226201734493130281418, 25750236424355735909778] |