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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 25 |
| 4 | 136 |
| 5 | 769 |
| 6 | 4300 |
| 7 | 24121 |
| 8 | 135184 |
| 9 | 757825 |
| 10 | 4247956 |
| 11 | 23812249 |
| 12 | 133480600 |
| 13 | 748232641 |
| 14 | 4194255964 |
| 15 | 23511117625 |
| 16 | 131792774176 |
| 17 | 738771155329 |
| 18 | 4141219588900 |
| 19 | 23213818753561 |
| 20 | 130126251314344 |
| 21 | 729429374039425 |
| 22 | 4088853757986796 |
| 23 | 22920279398302009 |
[0,1,4,25,136,769,4300,24121,135184,757825, 4247956,23812249,133480600,748232641,4194255964, 23511117625,131792774176,738771155329, 4141219588900,23213818753561,130126251314344, 729429374039425,4088853757986796, 22920279398302009] |