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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 25 |
| 3 | 154 |
| 4 | 943 |
| 5 | 5773 |
| 6 | 35344 |
| 7 | 216388 |
| 8 | 1324801 |
| 9 | 8110882 |
| 10 | 49657576 |
| 11 | 304020556 |
| 12 | 1861317163 |
| 13 | 11395616227 |
| 14 | 69767835259 |
| 15 | 427142397547 |
| 16 | 2615110919020 |
| 17 | 16010597772667 |
| 18 | 98022320649478 |
| 19 | 600125959188877 |
| 20 | 3674175070596919 |
| 21 | 22494548423870416 |
| 22 | 137719270059617428 |
[1,4,25,154,943,5773,35344,216388,1324801,8110882, 49657576,304020556,1861317163,11395616227, 69767835259,427142397547,2615110919020, 16010597772667,98022320649478,600125959188877, 3674175070596919,22494548423870416, 137719270059617428] |