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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 38 |
| 3 | 371 |
| 4 | 3474 |
| 5 | 30167 |
| 6 | 251674 |
| 7 | 2055232 |
| 8 | 16609480 |
| 9 | 133546783 |
| 10 | 1071058030 |
| 11 | 8579199454 |
| 12 | 68676536212 |
| 13 | 549584051869 |
| 14 | 4397359463098 |
| 15 | 35181623896924 |
| 16 | 281463983943136 |
| 17 | 2251755842615323 |
| 18 | 18014222625202438 |
| 19 | 144114484538737882 |
[4,38,371,3474,30167,251674,2055232,16609480, 133546783,1071058030,8579199454,68676536212, 549584051869,4397359463098,35181623896924, 281463983943136,2251755842615323, 18014222625202438,144114484538737882] |