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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 46 |
| 3 | 328 |
| 4 | 2374 |
| 5 | 17776 |
| 6 | 131548 |
| 7 | 973492 |
| 8 | 7213582 |
| 9 | 53429692 |
| 10 | 395740366 |
| 11 | 2931304708 |
| 12 | 21712231084 |
| 13 | 160822807612 |
| 14 | 1191219388318 |
| 15 | 8823392421952 |
| 16 | 65355090312238 |
| 17 | 484086844724824 |
| 18 | 3585643697043796 |
| 19 | 26558954938197124 |
| 20 | 196722861904335358 |
[4,46,328,2374,17776,131548,973492,7213582, 53429692,395740366,2931304708,21712231084, 160822807612,1191219388318,8823392421952, 65355090312238,484086844724824,3585643697043796, 26558954938197124,196722861904335358] |