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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 16 |
| 3 | 72 |
| 4 | 780 |
| 5 | 10144 |
| 6 | 181896 |
| 7 | 5346600 |
| 8 | 235865752 |
| 9 | 13718515360 |
| 10 | 1274547293612 |
| 11 | 182632256870400 |
| 12 | 35910248805192512 |
| 13 | 10519355362828229320 |
| 14 | 4986223632232028372840 |
| 15 | 3295839087283933350008520 |
[2,16,72,780,10144,181896,5346600,235865752, 13718515360,1274547293612,182632256870400, 35910248805192512,10519355362828229320, 4986223632232028372840,3295839087283933350008520] |