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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 10 |
| 6 | 60 |
| 7 | 35 |
| 8 | 336 |
| 9 | 1848 |
| 10 | 16080 |
| 11 | 33825 |
| 12 | 93280 |
| 13 | 539396 |
| 14 | 3856216 |
| 15 | 49390250 |
| 16 | 147478800 |
| 17 | 708041160 |
| 18 | 2354289744 |
| 19 | 18196716309 |
| 20 | 150847235040 |
| 21 | 2615953578700 |
| 22 | 9488756856040 |
| 23 | 57565330671310 |
| 24 | 296745669669768 |
| 25 | 1435526275752900 |
| 26 | 12231628020365000 |
[0,0,0,1,4,10,60,35,336,1848,16080,33825,93280, 539396,3856216,49390250,147478800,708041160, 2354289744,18196716309,150847235040,2615953578700, 9488756856040,57565330671310,296745669669768, 1435526275752900,12231628020365000] |