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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 38 |
| 3 | 504 |
| 4 | 8249 |
| 5 | 154036 |
| 6 | 3149326 |
| 7 | 68741880 |
| 8 | 1576163328 |
| 9 | 37548785408 |
| 10 | 922252542128 |
| 11 | 23222906277952 |
| 12 | 596981991939677 |
| 13 | 15616173859832740 |
| 14 | 414621835401615110 |
| 15 | 11150969618415168280 |
| 16 | 303278916800906999191 |
| 17 | 8330190277527648516572 |
| 18 | 230814933905555392525290 |
[1,4,38,504,8249,154036,3149326,68741880, 1576163328,37548785408,922252542128, 23222906277952,596981991939677,15616173859832740, 414621835401615110,11150969618415168280, 303278916800906999191,8330190277527648516572, 230814933905555392525290] |