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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 14 |
| 3 | 40 |
| 4 | 125 |
| 5 | 412 |
| 6 | 1540 |
| 7 | 6080 |
| 8 | 25580 |
| 9 | 111020 |
| 10 | 494066 |
| 11 | 2231960 |
| 12 | 10201365 |
| 13 | 47012620 |
| 14 | 218126120 |
| 15 | 1017565328 |
| 16 | 4769086955 |
| 17 | 22440958180 |
| 18 | 105967383690 |
| 19 | 501941663240 |
| 20 | 2384203613501 |
| 21 | 11353304737740 |
| 22 | 54186129705260 |
| 23 | 259150824770720 |
| 24 | 1241763877376990 |
| 25 | 5960465454101812 |
[4,14,40,125,412,1540,6080,25580,111020,494066, 2231960,10201365,47012620,218126120,1017565328, 4769086955,22440958180,105967383690,501941663240, 2384203613501,11353304737740,54186129705260, 259150824770720,1241763877376990,5960465454101812] |