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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 20 |
| 7 | 69 |
| 8 | 180 |
| 9 | 1930 |
| 10 | 12611 |
| 11 | 61051 |
| 12 | 566129 |
| 13 | 5179750 |
| 14 | 38348469 |
| 15 | 376547340 |
| 16 | 4169246332 |
| 17 | 41559058969 |
| 18 | 465750294781 |
| 19 | 5905176350849 |
| 20 | 72848728572828 |
| 21 | 946103621115633 |
| 22 | 13501160406995728 |
| 23 | 195518567272213262 |
| 24 | 2918439778172724571 |
| 25 | 46559546190633191495 |
[1,0,0,1,1,1,20,69,180,1930,12611,61051,566129, 5179750,38348469,376547340,4169246332,41559058969, 465750294781,5905176350849,72848728572828, 946103621115633,13501160406995728, 195518567272213262,2918439778172724571, 46559546190633191495] |