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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 15 |
| 2 | 105 |
| 3 | 495 |
| 4 | 1815 |
| 5 | 5577 |
| 6 | 15015 |
| 7 | 36465 |
| 8 | 81510 |
| 9 | 170170 |
| 10 | 335478 |
| 11 | 629850 |
| 12 | 1133730 |
| 13 | 1967070 |
| 14 | 3304290 |
| 15 | 5393454 |
| 16 | 8580495 |
| 17 | 13339425 |
| 18 | 20309575 |
| 19 | 30341025 |
| 20 | 44549505 |
| 21 | 64382175 |
| 22 | 91695825 |
| 23 | 128849175 |
| 24 | 178811100 |
| 25 | 245286756 |
| 26 | 332863740 |
| 27 | 447180580 |
[1,15,105,495,1815,5577,15015,36465,81510,170170, 335478,629850,1133730,1967070,3304290,5393454, 8580495,13339425,20309575,30341025,44549505, 64382175,91695825,128849175,178811100,245286756, 332863740,447180580] |