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| n | a(n) |
|---|---|
| 0 | 3 |
| 1 | 12 |
| 2 | 74 |
| 3 | 540 |
| 4 | 4178 |
| 5 | 33012 |
| 6 | 262874 |
| 7 | 2099340 |
| 8 | 16783778 |
| 9 | 134237412 |
| 10 | 1073800874 |
| 11 | 8590111740 |
| 12 | 68720008178 |
| 13 | 549757408212 |
| 14 | 4398051294074 |
| 15 | 35184386437740 |
| 16 | 281475019757378 |
| 17 | 2251799942825412 |
| 18 | 18014398896902474 |
| 19 | 144115189238117340 |
[3,12,74,540,4178,33012,262874,2099340,16783778, 134237412,1073800874,8590111740,68720008178, 549757408212,4398051294074,35184386437740, 281475019757378,2251799942825412, 18014398896902474,144115189238117340] |