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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 37 |
| 4 | 424 |
| 5 | 6241 |
| 6 | 113824 |
| 7 | 2460277 |
| 8 | 61504384 |
| 9 | 1746727201 |
| 10 | 55545439744 |
| 11 | 1955176596517 |
| 12 | 75470959673344 |
| 13 | 3169939381277761 |
| 14 | 143927870364811264 |
| 15 | 7024566555751464757 |
| 16 | 366742587098140770304 |
| 17 | 20394984041632355113921 |
| 18 | 1203587891190987380752384 |
| 19 | 75124090160952970927512997 |
[1,1,4,37,424,6241,113824,2460277,61504384, 1746727201,55545439744,1955176596517, 75470959673344,3169939381277761, 143927870364811264,7024566555751464757, 366742587098140770304,20394984041632355113921, 1203587891190987380752384, 75124090160952970927512997] |