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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 15 |
| 2 | 120 |
| 3 | 675 |
| 4 | 2940 |
| 5 | 10425 |
| 6 | 31320 |
| 7 | 82365 |
| 8 | 194520 |
| 9 | 420795 |
| 10 | 846600 |
| 11 | 1602975 |
| 12 | 2883060 |
| 13 | 4962165 |
| 14 | 8221800 |
| 15 | 13178025 |
| 16 | 20514480 |
| 17 | 31120455 |
| 18 | 46134360 |
| 19 | 66992955 |
| 20 | 95486700 |
| 21 | 133821585 |
| 22 | 184687800 |
| 23 | 251335605 |
| 24 | 337658760 |
| 25 | 448285875 |
| 26 | 588680040 |
| 27 | 765247095 |
[1,15,120,675,2940,10425,31320,82365,194520, 420795,846600,1602975,2883060,4962165,8221800, 13178025,20514480,31120455,46134360,66992955, 95486700,133821585,184687800,251335605,337658760, 448285875,588680040,765247095] |