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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 15 |
| 3 | 126 |
| 4 | 730 |
| 5 | 3270 |
| 6 | 11991 |
| 7 | 37450 |
| 8 | 102726 |
| 9 | 253485 |
| 10 | 573265 |
| 11 | 1205556 |
| 12 | 2384460 |
| 13 | 4475926 |
| 14 | 8031765 |
| 15 | 13858860 |
| 16 | 23106196 |
| 17 | 37372545 |
| 18 | 58837851 |
| 19 | 90421570 |
| 20 | 135971430 |
| 21 | 200486286 |
| 22 | 290376955 |
| 23 | 413769126 |
| 24 | 580852650 |
| 25 | 804281725 |
[1,15,126,730,3270,11991,37450,102726,253485, 573265,1205556,2384460,4475926,8031765,13858860, 23106196,37372545,58837851,90421570,135971430, 200486286,290376955,413769126,580852650,804281725] |