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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 12 |
| 3 | 50 |
| 4 | 180 |
| 5 | 745 |
| 6 | 3046 |
| 7 | 12531 |
| 8 | 52188 |
| 9 | 217004 |
| 10 | 902417 |
| 11 | 3754101 |
| 12 | 15614076 |
| 13 | 64942049 |
| 14 | 270106619 |
| 15 | 1123416589 |
| 16 | 4672495470 |
| 17 | 19433743246 |
| 18 | 80828359212 |
| 19 | 336179618100 |
| 20 | 1398231132013 |
| 21 | 5815492663346 |
| 22 | 24187671930371 |
| 23 | 100600845478730 |
[2,12,50,180,745,3046,12531,52188,217004,902417, 3754101,15614076,64942049,270106619,1123416589, 4672495470,19433743246,80828359212,336179618100, 1398231132013,5815492663346,24187671930371, 100600845478730] |