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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 5 |
| 4 | 18 |
| 5 | 85 |
| 6 | 346 |
| 7 | 1388 |
| 8 | 5454 |
| 9 | 21171 |
| 10 | 81250 |
| 11 | 309019 |
| 12 | 1166316 |
| 13 | 4372916 |
| 14 | 16300940 |
| 15 | 60456037 |
| 16 | 223201490 |
| 17 | 820709441 |
| 18 | 3006697550 |
| 19 | 10978569420 |
| 20 | 39965443098 |
| 21 | 145083078903 |
| 22 | 525337769138 |
| 23 | 1897732902967 |
| 24 | 6840395954992 |
| 25 | 24606162295316 |
[0,0,5,18,85,346,1388,5454,21171,81250,309019, 1166316,4372916,16300940,60456037,223201490, 820709441,3006697550,10978569420,39965443098, 145083078903,525337769138,1897732902967, 6840395954992,24606162295316] |