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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 15 |
| 3 | 90 |
| 4 | 630 |
| 5 | 3780 |
| 6 | 23220 |
| 7 | 139320 |
| 8 | 839160 |
| 9 | 5034960 |
| 10 | 30229200 |
| 11 | 181375200 |
| 12 | 1088367840 |
| 13 | 6530207040 |
| 14 | 39181942080 |
| 15 | 235091652480 |
| 16 | 1410554113920 |
| 17 | 8463324683520 |
| 18 | 50779973295360 |
| 19 | 304679839772160 |
| 20 | 1828079189798400 |
| 21 | 10968475138790400 |
| 22 | 65810851739735040 |
| 23 | 394865110438410240 |
| 24 | 2369190668072417280 |
| 25 | 14215144008434503680 |
| 26 | 85290864083258757120 |
[0,15,90,630,3780,23220,139320,839160,5034960, 30229200,181375200,1088367840,6530207040, 39181942080,235091652480,1410554113920, 8463324683520,50779973295360,304679839772160, 1828079189798400,10968475138790400, 65810851739735040,394865110438410240, 2369190668072417280,14215144008434503680, 85290864083258757120] |