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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 15 |
| 3 | 35 |
| 4 | 165 |
| 5 | 255 |
| 6 | 615 |
| 7 | 1815 |
| 8 | 1876 |
| 9 | 2636 |
| 10 | 2948 |
| 11 | 5380 |
| 12 | 5565 |
| 13 | 11235 |
| 14 | 28545 |
| 15 | 288380 |
| 16 | 903644 |
| 17 | 1807995 |
| 18 | 2486165 |
| 19 | 2674060 |
| 20 | 10538572 |
| 21 | 11791595 |
| 22 | 14145121 |
| 23 | 28558415 |
| 24 | 45153277 |
| 25 | 45682751 |
[4,15,35,165,255,615,1815,1876,2636,2948,5380, 5565,11235,28545,288380,903644,1807995,2486165, 2674060,10538572,11791595,14145121,28558415, 45153277,45682751] |