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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 18 |
| 4 | 128 |
| 5 | 840 |
| 6 | 5306 |
| 7 | 32802 |
| 8 | 200064 |
| 9 | 1209168 |
| 10 | 7261042 |
| 11 | 43394802 |
| 12 | 258401216 |
| 13 | 1534310232 |
| 14 | 9089538922 |
| 15 | 53748310338 |
| 16 | 317337926144 |
| 17 | 1871206403232 |
| 18 | 11021718519266 |
| 19 | 64859423566290 |
| 20 | 381371547195648 |
| 21 | 2240888478928488 |
| 22 | 13159108981577242 |
| 23 | 77232197285953890 |
| 24 | 453066998085075840 |
| 25 | 2656691258873376240 |
[0,0,2,18,128,840,5306,32802,200064,1209168, 7261042,43394802,258401216,1534310232,9089538922, 53748310338,317337926144,1871206403232, 11021718519266,64859423566290,381371547195648, 2240888478928488,13159108981577242, 77232197285953890,453066998085075840, 2656691258873376240] |