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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 32 |
| 5 | 120 |
| 6 | 528 |
| 7 | 2128 |
| 8 | 8960 |
| 9 | 36864 |
| 10 | 153472 |
| 11 | 635008 |
| 12 | 2635776 |
| 13 | 10922496 |
| 14 | 45300736 |
| 15 | 187800576 |
| 16 | 778731520 |
| 17 | 3228696576 |
| 18 | 13387309056 |
| 19 | 55506722816 |
| 20 | 230146834432 |
| 21 | 954246856704 |
| 22 | 3956565671936 |
| 23 | 16404954546176 |
| 24 | 68019305840640 |
| 25 | 282025965649920 |
[0,0,2,6,32,120,528,2128,8960,36864,153472,635008, 2635776,10922496,45300736,187800576,778731520, 3228696576,13387309056,55506722816,230146834432, 954246856704,3956565671936,16404954546176, 68019305840640,282025965649920] |