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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 15 |
| 4 | 675 |
| 5 | 7915 |
| 6 | 41310 |
| 7 | 145383 |
| 8 | 404185 |
| 9 | 959115 |
| 10 | 2029980 |
| 11 | 3939295 |
| 12 | 7139823 |
| 13 | 12245355 |
| 14 | 20064730 |
| 15 | 31639095 |
| 16 | 48282405 |
| 17 | 71625163 |
| 18 | 103661400 |
| 19 | 146798895 |
| 20 | 203912635 |
| 21 | 278401515 |
| 22 | 374248278 |
| 23 | 496082695 |
| 24 | 649247985 |
| 25 | 839870475 |
| 26 | 1074932500 |
| 27 | 1362348543 |
| 28 | 1711044615 |
[0,0,15,675,7915,41310,145383,404185,959115, 2029980,3939295,7139823,12245355,20064730, 31639095,48282405,71625163,103661400,146798895, 203912635,278401515,374248278,496082695,649247985, 839870475,1074932500,1362348543,1711044615] |