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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 23 |
| 4 | 173 |
| 5 | 1602 |
| 6 | 17575 |
| 7 | 222497 |
| 8 | 3188806 |
| 9 | 50988405 |
| 10 | 899222457 |
| 11 | 17329515172 |
| 12 | 362164300173 |
| 13 | 8155216185781 |
| 14 | 196789115887252 |
| 15 | 5064722539020379 |
| 16 | 138457553073641465 |
| 17 | 4006059432756066914 |
| 18 | 122284085809137076203 |
| 19 | 3926775294104305483621 |
| 20 | 132313462760902116605534 |
[1,1,4,23,173,1602,17575,222497,3188806,50988405, 899222457,17329515172,362164300173,8155216185781, 196789115887252,5064722539020379, 138457553073641465,4006059432756066914, 122284085809137076203,3926775294104305483621, 132313462760902116605534] |