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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 80 |
| 3 | 1408 |
| 4 | 23808 |
| 5 | 395264 |
| 6 | 6496256 |
| 7 | 106102784 |
| 8 | 1725759488 |
| 9 | 27987017728 |
| 10 | 452890460160 |
| 11 | 7316694892544 |
| 12 | 118053383700480 |
| 13 | 1902813588226048 |
| 14 | 30644438111879168 |
| 15 | 493182667873845248 |
| 16 | 7932561728196313088 |
| 17 | 127528427796392050688 |
| 18 | 2049363966872621416448 |
[0,4,80,1408,23808,395264,6496256,106102784, 1725759488,27987017728,452890460160,7316694892544, 118053383700480,1902813588226048, 30644438111879168,493182667873845248, 7932561728196313088,127528427796392050688, 2049363966872621416448] |